Tests: Added imgui-test engine hooks (experimental).

Merge branch 'master' into docking ...

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

Docking: Fixed Modal window from being dockable.

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.

Shutdown: Unlock font atlas before destroying context, so we can destroy a context between NewFrame and EndFrame if we wait (facilitate main loop structures). Internals: GetWindowScrollMaxX(), GetWindowScrollMaxY()

Merge branch 'viewport' into docking. 15ec78e Fixes the update of title buffer when docked in a leaf dock node with a single window. Added comment about overwriting DockIsActive in DockNodeUpdate(). ...

# Conflicts:
#	imgui.cpp

Internal: Moved stored window name update code to the first_begin_of_the_frame block. This will be useful in the Docking branch.

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.

Comments + internal using Tab Stop terminology (ImGuiItemFlags_NoTabStop instead of !ImGuiItemFlags_AllowKeyboardFocus)

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

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)

Docking: Removed context parameter from internal DockBuilderXXX api at it is expected we transition it to be public facing. (#2109)

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: Added ImGuiDockNodeFlags_NoOuterBorder, tweaked DockSpace demo to remove window border. Made docking splitter use the same standard setting as resizing from edges. (#2109)

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

Docking: Added ImGuiDockNodeFlags_NoDockingInsideDocRootNode flag. Honoring ImGuiDockNodeFlags_NoSplit in child node is already split (so we can use DockBuilder and then lock the layout). Added those options to the demo. (#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: Fixed crash using DockBuilderSplitNode(). (#2109)

Docking: Renamed io.ConfigDockingWithKeyMode to io.ConfigDockingWithShift.

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: Fixes for C++03 compilers.

Docking: Fixed extracting a dock node from a document root: document root should be preserved.