Merge branch 'master' into docking (enable range_select merge) ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

Internals: Tracking dummy select scope id (currently always zero) to facilitate merging of the range_select branch. (#1861)

Internals: Track ActiveIdHasBeenPressed (similar to ActiveIdHasBeenEdited). This is currently mostly for the benefit of the range_select branch. (#1861)

Docking: Extracted code into a DocknodeUpdateTabListMenu() functions + minor other changes.

Comments. Fix duplicate entries in About box. Synchronize a few small changes from Master branch.

Merged from Docking branch: Various small changes, comments, typos fixes, moved blocks. To reduce overall drift. Should be no-op.

Merge branch 'master' into docking ...

# Conflicts:
#	imgui.cpp

Docking: Builder: Added DockBuilderSetNodePos, DockBuilderSetNodeSize, allow DockBuilderAddNode creating floating node (dockspace requires ImGuiDockNodeFlags_Dockspace) (#2109)

Docking: VisibleWindow of a node spread its _NoMove attribute to the node (fixed dragging or undocking of dock node host from collapse button). (#2325, #2109)

Docking: Fixed faulty undocking of windows with the _NoMove flag. (#2325, #2109) ...

Whereas BeginAsDockableDragDropTarget could be reworked to filter, we simply set g.HoveredWindowUnderMovingWindow to be NULL when MovingWindow is not set, which was the initial intent.
Also fixed some comments and removed unused braces in TabItemEx().

Docking: Removed unnecessary ImGuiTabItemFlags_DockedWindow internal flag.

Viewport: Added ImGuiViewportFlags_NoFocusOnClick + support in imgui_impl_win32. Made windows with no decoration always set the _NoFocus flags. (#1542, #2117) ...

Fix e.g. clicking on protruding combo box stealing highlight from parent window with decoration.

Viewport: Popups by default merge into parent/host viewport as they have no decoration (same as menu/child). (#1542)

InputText: Fixed a bug where ESCAPE would be first captured by the Keyboard Navigation code. (#2321, #787)

imgui-test: Added extra item info callbacks. Using nav_bb for interactions when possible. Comments, Demo tweaks.

ImStrncpy: Fixed -Wstringop-truncation warning on GCC8 (#2323)

Docking: Comments and tidying up (should be no-op)

Added ImGuiDockNodeFlags_AutoHideTabBar. (#2109)

Docking: Exposing extra flag in Configuration panel. Moved some forgotten Changelog entries at the right place.

Fixed CloseCurrentPopup() on a child-menu of a modal incorrectly closing the modal. (#2308)

Silence XCode static analysis false positive (#2309)

Merge branch 'master' into docking ...

# Conflicts:
#	imgui.cpp

Revert "Added PushID(size_t sz) helper (may not be useful/meaningful for non C/C++ languages)." ...

This reverts commit 20bc06a.

Nav: Removed unnecessary test (always failing).

Using IM_UNUSED() macro.

Fix various XCode and PVS-Studio static analyzer warnings (#2309)

Added PushID(size_t sz) helper (may not be useful/meaningful for non C/C++ languages).

Docking: Fixed various border / padding related inconsistency with dock node vs floating windows. (#2109)

When resizing from an edge, the border is more visible and better follow the rounded corners. Border rendering moved to RenderOuterBorders so it can be called in a different order for docking. (#1495, #822)

Docking: Fixed overlapping issue with greyed out close button.