Docking: Fix io.ConfigWindowsMoveFromTitleBarOnly for docking branch.

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

Added io.ConfigWindowsMoveFromTitleBarOnly option. Still is ignored by window with no title bars (often popups). This affects clamping window within the visible area: with this option enabled title bars need to be visible. (#899) ...

Tweaked default value of style.DisplayWindowPadding from (20,20) to (19,19) so the default style as a value which is the same as the title bar height.

Renamed io.ConfigResizeWindowsFromEdges to io.ConfigWindowsResizeFromEdges and removed its [Beta] mark. Resizing windows from edge is now enabled by default (io.ConfigWindowsResizeFromEdges=true). Note that it only works _if_ the back-end sets ImGuiBackendFlags_HasMouseCursors, which the standard back-end do.

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

Viewport: Win32, GLFW, SDL: Clarified back-ends by using global mouse position direction. GLFW: disabled io.MouseHoveredViewport setting under Mac/Linux. (#1542, #2117) + various comments.

Viewport: Fix handling of PlatformRequestResize/PlatformRequestPos. when OS decoration are enabled via ImGuiConfigFlags_ViewportsDecoration .

Viewport: Fix handling of PlatformRequestResize/PlatformRequestPos. when OS decoration are enabled via ImGuiConfigFlags_ViewportsDecoration .

Docking: Adjusting the docking popup menu position so it tends to stay within the same viewport.

Docking: Documenting an issue. Renamed member of ImGuiDockFamily.

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.

Version 1.67 WIP + todo notes

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.

Docking: Focus fix (missing line in 8bac6d4)

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)

Docking: Fix generalizing the transition from loose windows to dock node so we can switch to single window dock node while transferring viewports (vs creating two viewports and dropping one). + Extracted DockContextGenNodeID out of DockContextAddNode().

Comments, tweak

Viewport: Minor tweaks, better struct layout.

Viewport: Fixed a viewport bug which led some popups to merge in underlying host viewport when they should be z-over their parent viewport.

Fixed IMGUI_API tag on ImFontAtlas::IsBuilt() preventing to build as DLL on some setups. (#2226)

Examples: DirectX10/11/12: Made imgui_impl_dx10/dx11/dx12.cpp link d3dcompiler.lib from the .cpp file to ease integration.

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

Somehow VS keeps modifying this GUID so I am going to playing along with it.