Examples: Renamed imgui_impl_sdl2.cpp to imgui_impl_sdl.cpp (#1870) + changelog bits

Examples: Renamed example folders. (#1870)

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: Documentation

Examples: Fixed Makefile, batch files.

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)

Examples: Added .. folder in include path to remove the awkward #include "../imgui_impl_xxx.h" statements.

Missing examples changelog bits and todo list

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/opengl2_example/imgui_impl_glfw_gl2.cpp
#	examples/opengl3_example/imgui_impl_glfw_gl3.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.h
#	examples/vulkan_example/imgui_impl_glfw_vulkan.cpp

Examples: OpenGL3: Removed unnecessary backup/restore of GL_ELEMENT_ARRAY_BUFFER_BINDING since this is part of the VAO state. (#1836)

Examples: iOS: Fixed missing call to CreateContext() + various shallow coding style tweaks. (#1835)

Examples: Comments about GLSL version not being the same as GL context version. (#1828)

Examples: GLFW: Made it possible to Shutdown/Init the backend again (by reseting the time storage properly). Changelog. Added to Vulkan example. (#1827)

Examples: GLFW* Make subsequent window creation possible.

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/opengl3_example/imgui_impl_glfw_gl3.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
#	imgui.cpp
#	imgui.h

Examples: OpenGL3: Trying to make the call to glBindSampler optional to make the example code easier to use/share with different context version. (#1806)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/sdl_opengl2_example/imgui_impl_sdl_gl2.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
#	imgui.cpp
#	imgui.h

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)

TODO list update + Changelog and comments for #1803.

Fixed clipboard paste memory leak in SDL examples. (#1803)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx9.cpp
#	imgui.cpp
#	imgui.h

Examples: DirectX9: Comments, updated changelog, notes about usage of imconfig.h (#1790, #1687)

add renderstate D3DRS_SHADEMODE for Dx9 impl ...

add backuping transform for Dx9 impl
(#1790, #1687)

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)

Added IMGUI_CHECKVERSION() macro to compare version string and data structure sizes in order to catch issues with mismatching compilation unit settings. (#1695, #1769)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/allegro5_example/imgui_impl_a5.cpp
#	examples/allegro5_example/imgui_impl_a5.h
#	examples/allegro5_example/imgui_impl_allegro5.cpp
#	examples/allegro5_example/imgui_impl_allegro5.h
#	examples/allegro5_example/main.cpp
#	examples/imgui_impl_allegro5.cpp
#	examples/imgui_impl_allegro5.h
#	imgui.cpp
#	imgui_internal.h