Merge branch 'docking2' into viewport_docking ...

# Conflicts:
#	examples/example_glfw_opengl2/main.cpp
#	examples/example_glfw_opengl3/main.cpp
#	examples/example_glfw_vulkan/main.cpp
#	examples/example_sdl_opengl3/main.cpp
#	examples/example_sdl_vulkan/main.cpp
#	examples/example_win32_directx10/main.cpp
#	examples/example_win32_directx11/main.cpp
#	examples/example_win32_directx12/main.cpp
#	imgui.cpp
#	imgui.h
#	imgui_demo.cpp
#	imgui_internal.h

Docking: Added Docking system. Enable with io.ConfigFlags |= ImGuiConfigFlags_DockingEnable. (Part 1) (#351)

Docking: Added ImVec2[] non const operator. Added ImStrSkipBlank. Reseting some values earlier in Begin. Added IMGUI_DEBUG_LOG() helper. Added docking source code section.

Tabs: Added BeginTabBar(), EndTabBar(), BeginTabItem(), EndTabItem() + demo. (#261, #351)

Added ImGuiWindowFlags_UnsavedDocument flags.

Version 1.66 WIP

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Version 1.65

Viewport: Making the code a little more sturdy (flag changes) + added descriptions. (#1542)

Merge branch 'master' into viewport + added viewport ConfigFlags/BackendFlags ...

# Conflicts:
#	imgui.cpp
#	imgui.h

Nav: Removed the [Beta] tag from various descriptions of the gamepad/keyboard navigation system. Although it is not perfect and will keep being improved, it is fairly functional and used by many. (#787)

Renamed io.OptCursorBlink/io.ConfigCursorBlink to io.ConfigInputTextCursorBlink. (#1427) + changed ImGuiIO layout.

Demo: Added a "Configuration" block to make io.ConfigFlags/io.BackendFlags more prominent.

Minor mostly inconsequential merges from Viewport + LoadIniSettingsFromMemory() entirely skip lines starting with ';'

Minor inconsequential merges from Master/Docking branches

Merge branch 'master' into viewport

Version 1.65 WIP

Merge branch 'master_164' into viewport_164 ...

# Conflicts:
#	imgui.cpp
#	imgui_draw.cpp
#	imgui_widgets.cpp

Version 1.64

Version 1.64 WIP

Version 1.64 WIP

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/example_glfw_opengl3/main.cpp
#	examples/imgui_impl_opengl3.cpp
#	imgui.cpp
#	imgui_internal.h

Version 1.63

Reordered some declarations in imgui.h (in prevision of 1.64 refactor)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui.h

ImFontAtlas Comments (#2042) + added ImGuiFontAtlas_None for consistency.

Removed obsolete redirection functions: CollapsingHeader() variation with 2 bools - marked obsolete in v1.49, May 2016.

Comments, demo

Renamed IsItemDeactivatedAfterChange() to IsItemDeactivatedAfterEdit() for consistency with new IsItemEdited() API. Kept redirection function (will obsolete fast as IsItemDeactivatedAfterChange() is very recent). (#820, #956, #1875, #2034)

Added IsItemEdited() to query if the last item modified its value (or was pressed). This is equivalent to the bool returned by most widgets. It is useful in some situation e.g. using InputText() with ImGuiInputTextFlags_EnterReturnsTrue. (#2034)