Viewport, Docking: Fixed incorrectly setting the ImGuiViewportFlags_NoInputs flag, affecting split docking node. (#2109)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui.h

Added ImGuiWindowFlags_NoMouseInputs which is basically the old ImGuiWindowFlags_NoInputs (essentially we have renamed ImGuiWindowFlags_NoInputs to ImGuiWindowFlags_NoMouseInputs). Made the new ImGuiWindowFlags_NoInputs encompass both NoMouseInputs+NoNav, which is consistent with its description. (#1660, #787)

Window: Added ImGuiWindowFlags_NoBackground flag for consistency and to ease creating new flag combinations. Added ImGuiWindowFlags_NoDecoration helper flag which is essentially NoTitleBar+NoResize+NoScrollbar+NoCollapse. (#1660)

Viewport: Exposed GetOverlayDrawList(ImGuiViewport* viewport) in public API. (#1542, #1660, #1878, etc.)

Merge branch 'master' into viewport ...

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

Revert using wchar_t functions (9cf94d5 + 2eaf5b0). Big mistake, wchar_t is not guaranteed to be 16-bits.

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

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()

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)

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)

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

Fixed extraneous static attribute. (#2105)

Fix missing IMGUI_API and mismatching namespace internal's CreateNewWindowSettings (#2105)

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.

Viewport: Misc tweaks.

Nav: Use Platform_SetWindowFocus when CTRL+Tabbing to another viewport.

Viewport: Increased threshold for setting ImGuiViewportFlags_NoFocusOnAppearing. (#1542), 2 doesn't seem enough with some docking setup.

Viewport: Fix an issue introduced on ~August 16, which would assert when viewport are disabled. Also made the DestroyPlatformWindow process more sturdy. (#1542)

Nav: Added a way for code to cancel Alt for menu toggle (ImGuiNavInput_KeyMenu_). Cancelling out on platform window. close request. (#1542, #787)