Merge branch 'examples_refactor2' into viewport (#1870) ...

# Conflicts:
#	examples/README.txt
#	examples/directx11_example/main.cpp
#	examples/directx12_example/main.cpp
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_glfw.cpp
#	examples/imgui_impl_opengl2.cpp
#	examples/imgui_impl_opengl2.h
#	examples/imgui_impl_opengl3.cpp
#	examples/imgui_impl_sdl2.cpp
#	examples/imgui_impl_sdl2.h
#	examples/imgui_impl_vulkan.cpp
#	examples/imgui_impl_vulkan.h
#	examples/imgui_impl_win32.cpp
#	examples/imgui_impl_win32.h
#	examples/opengl2_example/main.cpp
#	examples/opengl3_example/main.cpp
#	examples/sdl_opengl2_example/main.cpp
#	examples/sdl_opengl3_example/main.cpp
#	examples/sdl_vulkan_example/main.cpp
#	examples/vulkan_example/main.cpp
#	imgui.cpp
#	imgui.h

Big example binding refactor (manually imported from Viewport branch, stripped out of Viewport code). (#1870) ...

Read examples/README.txt for some details.
ImDrawData: Added DisplayPos, DisplaySize fields honored by all backends (not strictly necessary to honor just now, but doing it to be ahead)

Examples, Platform: Removed the call to ImGui::NewFrame() from the platform _NewFrame() function e.g. ImGui_ImplWin32_NewFrame(), ImGui_ImplSDL2_NewFrame(), ImGui_ImplGlfw_NewFrame(), etc. Moved to main.cpp for consistency. (#1542)

Viewport, Platform: Cleaned up xxx_UpdateMouseCursor() functions to make them more consistent. (#1542)

Viewport, Platform: Win32: Fixed handling of io.WantSetMousePos + added a bunch of comments. GLFW, SDL2: Added handling of io.WantSetMousePos. (#1542)

Viewport: Changed Monitor field to use Pos+Size (more consistent), changed FullMin,FullMax to MainPos,MainSize. Made main viewport accessible in PlatformIO on first frame. Fixed casing of ImGuiViewportFlags_TopMost flag. (#1542)

Viewport, Platform: Refresh monitor list (win32, glfw) + avoid calling GetWindowFocus before platform window creation to not require of backend to null-check things inconsistently. (#1542)

Viewport: Removed unnecessary fields (now that the coordinate system is consistent accross viewports): MouseRefPrevViewport, MouseClickedPosViewportId. (#1542)

Platform: Added platform_io.Platform_SetWindowFocus, Platform_GetWindowFocus function wrappers (unused yet). Exact specs tbd because our simplified concept of focus doesn't necessary match the more complex OS native concepts. (#1542)

Viewport: Fixed mouse hover flicker on mouse button release frame after moving a window. (#1542) ...

Platform: Clarifying some comments in back-ends.

Viewport, Platform: Fixed IME positioning for multi-viewport. Moved API from ImGuiIO to ImGuiPlatformIO. Because it is extremely unlikely to people redefined this API manually the moving-forward-breakage is ok. (#1542) ...

SDL2 ime support under Win32 never worked properly because of SDL interferences.

Viewport: Clamp windows within monitors + fallback rescue window when it is out of sight (e.g. removed monitor, changed resolution) + Win32: declare primary monitor at the beginning of the list. (#1542)

Viewport: Added ImGuiConfigFlags_ViewportsNoMerge flag (to enforce a platform window for all floating windows) + minor tidying up and addition of non-functional wip code.

Viewport, Platforms: SDL: Fixed initial focus click being ignored as a mouse button. GLFW: Fixed mouse cursor support for multi-viewport with GLFW 3.3 (current master) - somehow doesn't appear to work with GLFW 3.2 but I'm not too fussed about it. (#1542)

Viewport, Platform: Added work area in ImGuiPlatformMonitor. Renamed fields. (#1542)

Viewport: Switched to using unified platform-absolute mouse coordinates, which simplify lots of problems and simplify/reduce tricky conversions, makes ImVec2 less ambiguous. Fixed various viewport/windowing/popups/synchronization bugs. Settings on host-viewport are stored as relative (made settings decently compatible between viewport enable/disabled settings). Merged ImGuiViewport::Pos and ::PlatformPos. Tweaked thumbnails. Better, smaller code. (#1542)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_dx9.cpp
#	examples/opengl2_example/imgui_impl_glfw_gl2.cpp
#	examples/opengl3_example/imgui_impl_glfw_gl3.cpp
#	examples/sdl_opengl2_example/imgui_impl_sdl_gl2.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
#	examples/vulkan_example/imgui_impl_glfw_vulkan.cpp
#	imgui.cpp
#	imgui_internal.h

Viewport, Platform, DPI: Back-end store per-monitor DPI information in ImGuiPlatformMonitor. (#1542, #1676)

Viewport: Fixed DPI changing viewport from interfering with moving another window (disabling code) + metrics crash fix on closed viewport window + Windows 10 call to SetThreadDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2) for DPI, with no noticeable improvements. (#1542, #1676)

Viewport, Platform: Added ImGuiViewportFlags_TopMost that will be used by tooltip window (without it, clicking and holding the window emitting the tooltip would move the tooltip to the back) + GLFW backend fixes for non-win32 platforms. (#1542)

Viewport: Merged ImGuiPlatformData into ImGuiPlatformIO. Comments. (#1542)

Viewport, Platform: Added a way to register monitor bounds to imgui so they can be used to clamp individual-viewport tooltips/popups so they don't straddle monitors. (#1542)

Viewports, DPI: Renamed config flags. (#1542)

Viewport: Popups, Tooltips can individually request no task bar icons to the platform layer. (#1542)

Examples, Platform, Viewport: Fixed inconsistent window ownership issues. Added comments. Made Win32/SDL back-ends track ownership.

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_dx9.cpp
#	examples/opengl2_example/imgui_impl_glfw_gl2.cpp
#	examples/opengl3_example/imgui_impl_glfw_gl3.cpp
#	examples/sdl_opengl2_example/imgui_impl_sdl_gl2.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
#	examples/vulkan_example/imgui_impl_glfw_vulkan.cpp
#	imgui.cpp
#	imgui.h
#	imgui_internal.h

Viewport, Platform, Examples: Added support for transparent window via PlatformIO Platform_SetWindowAlpha (#1542) + fixes for GLFW 3.3

Viewport: Comments about honoring ImGuiViewportFlags_NoInputs and MouseHoveredViewport. (#1542)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_dx9.cpp
#	examples/opengl2_example/imgui_impl_glfw_gl2.cpp
#	examples/opengl3_example/imgui_impl_glfw_gl3.cpp
#	examples/sdl_opengl2_example/imgui_impl_sdl_gl2.cpp
#	examples/sdl_opengl2_example/imgui_impl_sdl_gl2.h
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.h
#	imgui.cpp

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_dx9.cpp
#	examples/opengl2_example/imgui_impl_glfw_gl2.cpp
#	examples/opengl3_example/imgui_impl_glfw_gl3.cpp
#	examples/sdl_opengl2_example/imgui_impl_sdl_gl2.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
#	examples/vulkan_example/imgui_impl_glfw_vulkan.cpp
#	imgui.h