Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui.h

Viewport: Corrected/clarified comments. Moved RenderPlatformWindowsDefault() next to UpdatePlatformWindow(). Removed unnecessary flag check.

IO: Realigned all fields, very minor comments change. This is nearly a no-op if you don't ignore Spaces.

IO: Added BackendPlatformUserData, BackendRendererUserData, BackendLanguageUserData void* for storage use by back-ends. (#2004 + for cimgui)

Various user-facing comments

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Internals: Popup related comments. Renamed the misleading internal ClosePopup() function. Added bool* test to BeginPopupModal in demo.

Viewport, DPI: Now using DpiScale from the ImGuiPlatformMonitor array instead of calling Platform_GetWindowDpiScale() before the platform window creation. Might even tentatively see if things work out without Platform_GetWindowDpiScale. (#1676)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.h

Comments, minor tweaks.

Demo: Using Tabs in Style Editor and Simple Layout example. + Adding missing early out in About and Documents examples.

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

Added BETA api for Tab Bar/Tabs widgets. (#261, #351) (merged this feature from the from Docking branch so it can be used earlier as as standalone feature) ...

- Added BeginTabBar(), EndTabBar(), BeginTabItem(), EndTabItem(), SetTabItemClosed() API.
- Added ImGuiTabBarFlags flags for BeginTabBar().
- Added ImGuiTabItemFlags flags for BeginTabItem().
- Style: Added ImGuiCol_Tab, ImGuiCol_TabHovered, ImGuiCol_TabActive, ImGuiCol_TabUnfocused, ImGuiCol_TabUnfocusedActive colors.
- Demo: Added Layout->Tabs demo code.
- Demo: Added "Documents" example app showcasing possible use for tabs.

Added ImGuiWindowFlags_UnsavedDocument window flag to append '*' to title without altering the ID, as a convenience to avoid using the ### operator. (merged from Docking branch)

Using named flags instead of 0 + shallow formatting tweaks from other branches.

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_demo.cpp

Added io.ConfigWindowsMoveFromTitleBarOnly option. Still is ignored by window with no title bars (often popups). This affects clamping window within the visible area: with this option enabled title bars need to be visible. (#899) ...

Tweaked default value of style.DisplayWindowPadding from (20,20) to (19,19) so the default style as a value which is the same as the title bar height.

Renamed io.ConfigResizeWindowsFromEdges to io.ConfigWindowsResizeFromEdges and removed its [Beta] mark. Resizing windows from edge is now enabled by default (io.ConfigWindowsResizeFromEdges=true). Note that it only works _if_ the back-end sets ImGuiBackendFlags_HasMouseCursors, which the standard back-end do.

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

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.

Version 1.67 WIP + todo notes

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp

Viewport: Minor tweaks, better struct layout.

Fixed IMGUI_API tag on ImFontAtlas::IsBuilt() preventing to build as DLL on some setups. (#2226)

Version 1.67 WIP (again, this time IMGUI_VERSION_NUM has leeway for another hot-fix).

Merge branch 'master' into viewport ...

# Conflicts:
#	docs/CHANGELOG.txt
#	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_opengl3.cpp
#	examples/imgui_impl_sdl.cpp
#	examples/imgui_impl_vulkan.cpp
#	examples/imgui_impl_win32.cpp
#	imgui.h
#	imgui_demo.cpp

Version 1.66b (will revisit how to change IMGUI_VERSION_NUM across versions, this commit reduces the numerical IMGUI_VERSION_NUM compared to the commit on Nov 22).

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

Added ShowAboutWindow(), About Window now showing various config/build information.

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