Merge branch 'master' into docking ...

# Conflicts:
#	imgui.cpp
#	imgui_demo.cpp
#	imgui_widgets.cpp

Tabs: Fixed support for drag and drop ImGuiButtonFlags_PressedOnDragDropHold. (#261) incorrectly missing from the merge from Docking branch.

BeginTabBar: Fix to push the expected ID into the ID stack (instead of a hash's hash). (#261)

Merge branch 'viewport' into docking ...

# Conflicts:
#	docs/TODO.txt
#	imgui.cpp
#	imgui.h
#	imgui_demo.cpp
#	imgui_draw.cpp
#	imgui_internal.h
#	imgui_widgets.cpp

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.

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

Merge branch 'viewport' into docking + moved io.ConfigFlags ImGuiConfigFlags_DockingNoSplit to io.ConfigDockingNoSplit ...

# Conflicts:
#	imgui.cpp
#	imgui.h
#	imgui_demo.cpp

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_demo.cpp

Tests: Adding imgui-test engine hooks (experimental) to provide missing widget state to the testing system.

Tabs: Fixed crash when using TabItem in a regular (non-docking) tab bar. (#2231)

Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui.cpp

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

Internals: Nav: Added ImGuiNavLayer_ to clarify semantic of previously integer NavLayer values, and not pretend that increment/decrement operators on them super flexible. + Storage tweaks.

Docking: Added io.ConfigDockingTabBarOnSingleWindows option (mostly made possible by the previous fixes). ...

Note that dock node have regressions compared to current floating window: no collapse, no auto-resize, resize grip under the scrollbar, border issues, general overhead. Will tackle those.

Merge branch 'viewport' into docking ...

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

Merge branch 'master' into viewport ...

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

Docking: Another attempt at tidying the inconsistent focus / tab bar reordering issues, and toward generalizing single window dock nodes. (#2109)

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

Merge branch 'viewport' into docking ...

# Conflicts:
#	docs/CHANGELOG.txt

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).

Merge branch 'viewport' into docking

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

Separator: Fixed Separator() outputting an extraneous empty line when captured into clipboard/text/file.

Docking: Added internal DockBuilderGetCentralNode(). Fixed being unable to undock whole node from dock button in DockSpace with a central node. (#2109)

Merge branch 'viewport' into docking ...

# Conflicts:
#	docs/CHANGELOG.txt
#	imgui.cpp
#	imgui_internal.h

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp

Version 1.67 WIP

Merge branch 'viewport' into docking ...

# Conflicts:
#	docs/CHANGELOG.txt
#	imgui_widgets.cpp