Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp

Renamed extra_flags to flags in InputXXX parameters.

InputFloat: When using ImGuiInputTextFlags_ReadOnly the step buttons are disabled. (#2257)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Window, Focus, Popup: Fixed an issue where closing a popup by clicking another window with the _NoMove flag would refocus the parent window of the popup instead of the newly clicked window.

Internals: Popups: Renamed CurrentPopupStack to BeginPopupStack which is much less ambiguous.

Internals: Popups: EndMenu() calls ClosePopupToLevel(g.CurrentPopupStack.Size) which is more correct.

Tests: Changed prototype of ImGuiTestEngineHook_ItemAdd to match functions called in same spot. Made ButtonBehavior submit fallback item info if ItemAdd() was not called (for resize grips, resize borders, scrollbar, columns, etc.)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.h

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 '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 '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.

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.

Merge branch 'master' into viewport ...

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

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).

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.

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp

Version 1.67 WIP

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Version 1.66

Merge branch 'master' into viewport + comments ...

# Conflicts:
#	examples/imgui_impl_opengl3.cpp
#	imgui.cpp

Viewport: BeginMainMenuBar(): explicitly set viewport to avoid creating new one when ImGuiConfigFlags_ViewportsNoMerge is set + misc shallow changes.