Merge branch 'viewport' into docking ...

# Conflicts:
#	docs/CHANGELOG.txt
#	imgui.cpp
#	imgui_draw.cpp

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

Examples: OpenGL2: Added (yet another) comment/instruction against using opengl2 with modern OpenGL. (#2297)

Removed trailing spaces (#2038, #2299)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_win32.cpp

Examples: Win32: Using wc.lpszClassName instead of duplicating the literal. + tweak README format.

Examples: Win32: Added support for mouse buttons 4 and 5 via WM_XBUTTON* messages. (#2264)

Examples: Win32: Fix for older Windows SDK.

Merge branch 'viewport' into docking ...

# Conflicts:
#	docs/CHANGELOG.txt

Merge branch 'master' into viewport ...

# Conflicts:
#	docs/CHANGELOG.txt
#	examples/imgui_impl_win32.cpp
#	imgui_demo.cpp

Examples: Win32: Using IsChild() to be compatible with windows created within a parent. (#1951, #2087, #2156, #2232)

Examples: DirectX9: Explicitly disable fog (D3DRS_FOGENABLE) before drawing in case user state has it set. (#2288, #2290)

Examples: DirectX12: Targeting 10.0.14393.0 instead of 10.0.16299.0 (available on AppVeyor, and higher version doesn't seem necessary).

Merge branch 'viewport' into docking

Merge branch 'master' into viewport ...

# Conflicts:
#	docs/CHANGELOG.txt
#	examples/imgui_impl_win32.cpp
#	examples/imgui_impl_win32.h

Examples: Win32: Added support for XInput games (if ImGuiConfigFlags_NavEnableGamepad is enabled).

Examples: Win32: Using GetForegroundWindow() instead of GetActiveWindow() to be compatible with windows created in a different thread. (#1951, #2087, #2156, #2232) [many people]

Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui_internal.h
#	imgui_widgets.cpp

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui.h
#	imgui_internal.h

Examples: Allegro 5: Properly destroy all globals on shutdown. (#2262)

Examples: Downgrading projects to xcode 9.2 (maybe 8.0) (#2134) ...

* example_apple_opengl2: The deployment target was set to 10.12 from XCode 9.2.
* imgui_impl_metal: header not found by XCode 9.2.
* example_apple_metal: The deployment target was set to 10.12 from XCode 9.2.

Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui.cpp
#	imgui.h
#	imgui_internal.h

Viewport: Added ImGuiWindowClass / SetNextWindowClass() (concept imported from Docking ImGuiDockFamily), which currently allows to overwrite viewport flags on a per-window basis. Exposed FindViewportByID(). Win32: Support for ParentViewportId. (#1542)

Viewport: Win32: Workaround to the fact that ::WindowFromPoint() seems to return Windows using ImGuiViewportFlags_NoInputs / HTTRANSPARENT when dragging nearby the platform title bar. This is to allow using platform decoration. I don't understand this well atm. (#1542)

Viewport: Added Platform_UpdateWindow hook for general purpose: Rework Win32 code to reflect viewport flags changes into Win32 while the window is active.

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp

Examples: Comments about GLFW/SDL versions

Tweaked asserts

Viewport: Misc comments following user feedbacks..

Fix merge in Docking branch, remove ConfigDockingWithShift flag from DX11 example + misnamed function.