Docking: Added DockBuilderForkNode() primitive for usage for user code to fork/copy entire layouts. This will probably need to be added to as I find ways to migrate patterns from user code to the library. Added IMGUI_DEBUG_DOCKING_INI helper to facilitate debugging. (+1 squashed commits)

Docking: Minor renaming. DockContextAddNode() uses 0 as marker for automatic ID selection + TODO update and moved docking entries to docs/TODO.txt

Docking: Renamed SetNextWindowDock() to SetNextWindowDockId(). Added GetWindowDockId().

Docking: Reworked SetNextWindowUserType() as SetNextWindowDockFamily(), allowing multiple scene to be tagged with their scene id and not receive tabs from other scene + persistent storage for family id to allow for docking tree fork/remap.

ImVector: Fixed a oddly unqualified return type in the assignment operator (I assume C++ handles it nicely as this never warned anywhere, but it is completely unintentional).

Docking: Renamed ImGuiDockSpaceFlags to ImGuiDockNodeFlags. Clarified in comments/demos that DockSpace creates a Node. Renamed IsExplicitRoot to IsDockSpace. Assert against explicitly calling DockSpace twice in a frame.

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

Docking: Changed DockSpace() signature to take an ID, as ID will frequently be used by other API it makes more sense to let the user compute it.

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)

Docking: Added ImGuiDockSpaceFlags_KeepAliveOnly, important for multiple level of tabs. (also renamed ImGuiDockFlags to ImGuiDockSpaceFlags.)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

Docking: Added SetNextWindowUserType() + user type filtering in dockspace and window merging. Added DockSpace() flag ImGuiDockFlags_NoSplit. Renaming. Reworked the DockNodeUpdateFindOnlyNodeWithWindows code so DockNodeUpdate can access the first window.

Docking: io.ConfigResizeWindowsFromEdges default to true in Docking branch. Moved code in BeginTabItem().

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