Merge branch 'master' into docking ...

# Conflicts:
#	examples/imgui_impl_glfw.cpp
#	examples/imgui_impl_sdl.cpp

Examples: GLFW, SDL: Preserve DisplayFramebufferScale when main viewport is minimized. (This is particularly useful for the viewport branch because we are not supporting per-viewport frame-buffer scale. It fixes windows not refreshing when main viewport is minimized.) (#2416)

Viewport: SDL: Inherit SDL_WINDOW_ALLOW_HIGHDPI flag from main viewport. (#2306)

Examples: SDL: Fix for Emscripten/Android/iOS on Docking branch.

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/example_sdl_vulkan/main.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_glfw.cpp
#	examples/imgui_impl_sdl.cpp
#	examples/imgui_impl_vulkan.h
#	imgui.cpp

Removed trailing spaces (#2038, #2299)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp

Examples: Comments about GLFW/SDL versions

Tweaked asserts

Build fix for master.

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp

Examples: SDL: Avoid testing for SDL_GetKeyboardFocus() on Android and iOS (like Emscripten). (#421)

Examples: SDL: Fixed compilation for SDL 2..0.3 and less (running on our test servers) and clarified a bit of the messy situation. Followup to 8dd83c5. (#1542, #2117)

Examples: SDL: SDL_GetMouseState() seems problematic, movements feels laggy in the non-viewport code path. (#1542, #2117)

Viewport: Win32, GLFW, SDL: Clarified back-ends by using global mouse position direction. GLFW: disabled io.MouseHoveredViewport setting under Mac/Linux. (#1542, #2117) + various comments.

Fixed typo.

About, IO: Added io.BackendPlatformName, io.BackendRendererName for informational/QA purpose.

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_glfw.cpp
#	examples/imgui_impl_opengl2.cpp
#	examples/imgui_impl_opengl3.cpp
#	examples/imgui_impl_sdl.cpp
#	examples/imgui_impl_win32.cpp
#	imgui.h

About, IO: Added io.BackendPlatformName, io.BackendRendererName for informational/QA purpose.

Viewport: imgui_impl_sdl2: Added support for PlatformIO Platform_SetWindowAlpha.

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp

Examples: SDL: changed the signature of ImGui_ImplSDL2_ProcessEvent() to use a const SDL_Event*. (#2187)

Viewport: Added support for minimized window which caused problem when ImGuiBackendFlags_HasMouseHoveredViewport was not supported. (#1542) + todo

Examples: SDL: Fixed usage of SDL_GetDisplayDPI (#2137, #1676)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp
#	imgui.cpp

Fix spacing in imgui_imp_sdl example (#2111)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_win32.cpp
#	examples/imgui_impl_win32.h
#	imgui.cpp

Examples: Referring to missing gamepad support in back-end that are missing it.

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx9.cpp
#	examples/imgui_impl_opengl2.cpp
#	examples/imgui_impl_opengl3.cpp
#	examples/imgui_impl_vulkan.cpp

Examples: Using "dear imgui" terminology in all examples headers/comments + fix minor typo.