Revert part of change from 5536eded. Fixed drag and drop in docking branch. (#2331, reopening #2325)

Removed io.DisplayVisibleMin/DisplayVisibleMax (which were marked obsolete and removed from viewport/docking branch already).

Removed io.DisplayVisibleMin/DisplayVisibleMax (which were marked obsolete and removed from viewport/docking branch already).

Examples: Made imgui_impl_win32 drag gdi32.lib for GetDeviceCaps(). (#2327)

Examples: OpenGL3: Using GLSL 4.10 shaders for any GLSL version over 410 (e.g. 430, 450). (#2329) [@BrutPitt]

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: Minor changes to TreeNodeBehavior() and Selectable() for the benefit of fhe range_select branch. (#1861)

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

Fixed Clang/Win32 warning.

Merge branch 'master' into docking ...

# Conflicts:
#	imgui.cpp
#	imgui.h
#	imgui_internal.h

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.

Merged from Docking branch: non-const ImVec2[] operator.

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.

Fixed doc typo (#2326)

Updating supporter list.

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)

Internals: InputScalarAsWidgetReplacement: Fixed seemingly unnecessary calling of SetActiveID/SetHoveredID every frame, which in turns allow us to remove the g.ActiveIdAllow/Block settings duplicated.

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

InputText: Fixed a bug where ESCAPE would not restore the initial value in all situations. (#2321) [@relick]

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)