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. (Part 3) (#351)

Docking: Added Docking system. (Part 2) (#351)

Docking: Added empty skeleton/sections to facilitate diff/patch of incoming code (otherwise git gives us a messier patch).

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.

Internals: Windows hidden with HiddenFramesRegular (but NOT HiddenFramesForResize) preserve their SizeContents, so restoring a auto-resize window after it's been hidden by tabs won't reset its size for a frame. Arguable. Let's see how it goes. (Followup to b48e295)

Internals: Split RenderTextClipped into two functions.

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)

Refactor: Moved ImFile functions. (#2036)

Refactor: Moved one indentation level in the bulk of the ShowMetricsWindow() function. Should appear as a small diff if whitespaces changes are ignored. (#2036)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Refactor: moved low-layout helpers to imgui_widgets.cpp (Spacing, Dummy, NewLine, Separator, etc.) (#2036)

Internals: Refactor: Moved render functions to their own section. (#2036)

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

Viewport: Moved code following refactor. (#2036, #1542)

Fixed a build issue with non-Cygwin GCC under Windows.