Merge branch 'viewport' into docking

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_win32.cpp
#	examples/imgui_impl_win32.h
#	imgui.cpp

ImDrawList: Fixed AddConvexPolyFilled() undefined behavior when passing points_count smaller than 3, in particular, points_count==0 could lead to a memory stomp if the draw list was previously empty.

Fixed bad merge (a82be53) where we lost the version number in Docking branch + moved Docking related API together for now.

Merge branch 'viewport' into docking ...

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

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx9.cpp
#	examples/imgui_impl_opengl2.cpp
#	examples/imgui_impl_opengl3.cpp
#	examples/imgui_impl_vulkan.cpp

Internals: Replace unsigned short with ImWchar when dealing with character storage. (#2078)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

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)

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

Version 1.66 WIP

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Version 1.65

Renamed stb_truetype.h to imstb_truetype.h, stb_textedit.h to imstb_textedit.h, and stb_rect_pack.h to imstb_rectpack.h. (#1718, #2036) ...

If you were conveniently using the imgui copy of those STB headers in your project, you will have to update your include paths.
The reason for this change is to avoid conflicts for projects that may also be importing their own copy of the STB libraries. Note that imgui's copy of stb_textedit.h is modified.

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Refactor: Tweaked and improved the sectioning to facilitate grepping/moving around and applied to all files. (#2036)

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

Tweak comments and indexes

Refactor: Moved Scrollbar function from imgui.cpp to imgui_widgets.cpp, added file index (#2036)

Refactor: Moved Scrollbar function from imgui.cpp to imgui_widgets.cpp, added file index (#2036)

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

Internals: Tidying up, moving helpers to imgui_internal.h (in prevision of 1.64 refactor)