Merge branch 'master' into docking ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp
#	imgui.cpp
#	imgui_internal.h

RenderText(), InputTextMultiline(): Optimization for large text by using memchr, wmemchr, wcschr when appropriate.

Renamed misc/stl/imgui_stl.h,.cpp to misc/cpp/imgui_stdlib.h in prevision for other files.(#2035, #2096) ...

Added misc/README file.

TextUnformatted: Using memchr(), fixed not properly testing for text_end bound + comments. ...

Internals: Added ImStreolRange() + used in LogRenderedText() + comments.

ImGuiTextBuffer: Avoid heap allocation when empty.

Viewport: Added ImGuiConfigFlags_ViewportsDecoration to re-enable platform decoration (#1542)

Docking: Kept ImGuiDockNodeFlags_PassthruDockspace and removed ImGuiDockNodeFlags_PassthruInEmptyNodes, ImGuiDockNodeFlags_RenderWindowBg. Doesn't include ImGuiDockNodeFlags_NoDockingInCentralNode. (#2109)

Update README.md

Update README.md

Examples: DirectX10, DirectX11: Removed seemingly unnecessary calls to invalidate and recreate device objects in the WM_SIZE handler. (#2088)

Docking: Added ImGuiDockNodeFlags_PassthruDockspace mode (subdivided in three flags: ImGuiDockNodeFlags_NoDockingInCentralNode, ImGuiDockNodeFlags_PassthruInEmptyNodes, ImGuiDockNodeFlags_RenderWindowBg). Added internal facility for register a rectangular hit-test hole in window. Updated DockSpace demo accordingly. (#2109)

Docking: Renamed "DocRoot/DocumentRoot" to "CentralNode", more self explanatory. Moved Splitter update higher up in DockNodeUpdate() + minor misc tweak. (#2109)

Docking: Fixed DockSpace() child window displaying a scrollbar behind the node backgrounds. Rename ImGuiCol_DockingBg to ImGuiCol_DockingEmptyBg. Added ImGuiDockNode::IsLeaftNode(). (#2109)

Merge branch 'viewport' into docking

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Window, Inputs: Fixed resizing from edges when io.MousePos is not pixel-rounded by rounding mouse position input. (#2110)

Window: Resizing from edges (with io.ConfigResizeWindowsFromEdges Beta flag) extends the hit region of root floating windows outside the window, making it easier to resize windows. Resize grips are also extended accordingly so there are no discontinuity when hovering between borders and corners. (#1495, #822, #2110)

Docking: Renamed io.ConfigDockingWithKeyMode to io.ConfigDockingWithShift.

Fixed typo. (#2108, #2083)

Drag and Drop: Added GetDragDropPayload() to peek directly into the payload (if any) from anywhere. (#143)

Docking: Better tracking of current dock id for inactive and uncreated windows (in settings etc.). + Fixed assert when docking a single-visible leaf node of a hierarchy into another

Docking: Reworked DockContextPruneUnusedSettingsNodes() to prune entire unused trees.

Merge branch 'viewport' into docking

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_win32.cpp
#	examples/imgui_impl_win32.h
#	imgui.cpp

Renamed SetScrollHere() to SetScrollHereY(). Kept redirection function (will obsolete).

BeginChild(): Fixed BeginChild(const char*, ...) variation erroneously not applying the ID stack to the provided string to uniquely identify the child window. This was undoing an intentional change introduced in 1.50 and broken in 1.60. (#1698, #894, #713) + reworked the Begin/BeginChild comments in imgui.h.

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

ImDrawList: Fixed AddConvexPolyFilled() undefined behavior when passing points_count smaller than 3, in particular, points_count==0 could lead to a memory stomp if the draw list was previously empty.

ArrowButton(): Fixed arrow shape being horizontally misaligned by (FramePadding.y-FramePadding.x) if they are different. ...

Demo: Added extra usage of AlignTextToFramePadding() in a more visible section.

Fix file names (#2083)