Merge branch 'master' into docking ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx9.cpp
#	examples/imgui_impl_opengl3.cpp
#	imgui.h
#	imgui_demo.cpp

Renamed ImGuiBackendFlags_HasVtxOffset to ImGuiBackendFlags_RendererHasVtxOffset to match naming convention already used in viewport/docking branch. (#2591) + Fix OpenGL3 code missing flag.

Merge branch 'master' into docking ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx10.h
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx11.h
#	examples/imgui_impl_dx9.cpp
#	examples/imgui_impl_dx9.h
#	examples/imgui_impl_opengl3.cpp
#	examples/imgui_impl_opengl3.h
#	examples/imgui_impl_osx.h
#	examples/imgui_impl_osx.mm
#	imgui.cpp
#	imgui.h
#	imgui_demo.cpp
#	imgui_internal.h

Examples/Backends: DirectX9/10/11/12, Vulkan, OpenGL3 (Desktop GL only): Added support for large meshes (64k+ vertices) with 16-bits indices, enable 'ImGuiBackendFlags_HasVtxOffset' config flag in back-end. (#2591)

ImDrawList: Added ImDrawCmd::VtxOffset value to support large meshes (64k+ vertices) using 16-bits indices. To enable the feature, the renderer back-end needs to set 'io.BackendFlags |= ImGuiBackendFlags_HasVtxOffset' and honor the ImDrawCmd::VtxOffset field. Otherwise the value will always be zero. This has the advantage of preserving smaller index buffers and allowing to execute on hardware that do not support 32-bits indices. ...

ImDrawList: Added ImDrawCmd::IdxOffset value, equivalent to summing element count for each draw command. This is provided for convenience and consistency with VtxOffset. (#2591)

ImDrawList: Store initial flags for the frame in ImDrawListSharedData, reducing code duplication in setting up the flags.

CollapsingHeader: When a close button is enabled, better clip the label to avoid overlap. (#600)

Fonts: Added some details about using custom colorful icons.

Internal: Renamed InnerMainRect to InnerVisibleRect. Printing coordinates in Metrics window.

Changelog, minor tweaks. (#2585)

Examples: imgui_impl_osx: Added mouse cursor support. (#2585, #1873)

Docking: Fixed DockBuilderRemoveNode() from overwriting other parent node flags when trying to move the CentralNode flag.

Docking: Saving local _NoResize flag. (#2583)

Added full "Dear ImGui" prefix to the title of "Dear ImGui Demo" and "Dear ImGui Metrics" windows. Shortened amount of nodes in columns>tree demo.

Docking: Saving the NoTabBar, NoWindowMenuButton, NoCloseButton fields of dock node into the .ini file. Added them to the Metrics window. (#2583, #2423, #2109).

Comments, todo entries, moved ImGuiSelectableFlagsPrivate in higher ranges to match others.

ColorEdit: Fixed the color picker popup only displaying inputs as HSV instead of showing multiple options. (#2587, broken in 1.69 by #2384).

Docking: Clarified terminology of docking/tablist/collapse button into Window Menu button matching master. Added private ImGuiDockNodeFlags_NoWindowMenuButton, ImGuiDockNodeFlags_NoCloseButton flags. (#2583, #2109)

Examples: imgui_impl_opengl3: Fix empty printout on shader load. (#2584) ...

Fixed minor bug in CheckShader and CheckProgram

The log_length reported by 
glGetProgramiv(handle, GL_INFO_LOG_LENGTH, &log_length)
will at least return 1, since the string delimiter is also counted.

The old version would always print and empty string to stderr. This is annoying in the emscripten port, since it prints a red error message to the Javascript console. The new version fixes this behavior.

Docking: Honor style.WindowMenuButtonPosition setting in docking node.

Merge branch 'master' into docking ...

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

Style: Added style.WindowMenuButtonPosition (left/right, defaults to ImGuiDir_Left) to move the collapsing/docking button to the other side of the title bar.

Internal: CloseButton takes an upper-left corner + a size to be consistent with similar widgets.

Internals: Extracted some of the tab bar shrinking code into a ShrinkWidths() function so columns/table can use it.

Fixed InputScalar, InputScalarN, SliderScalarN, DragScalarN with non-visible label from inserting style.ItemInnerSpacing.x worth of trailing spacing.

Merge branch 'master' into docking ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

Internals: Added InnerWorkRect equal to old InnerClipRect, added InnerWorkRectClipped actually clipped.

Version tag is 1.71 WIP oops

Fix OuterRectClipped not being clipped correctly, which resulted in child window outside visible bound to not be marked with SkipItems. Broken in b50c61c. ...

+ Comments on InnerClipRect being misleading. Demo: Tweak to sizing of child window in the Layout->Scrolling section.

Merge branch 'master' into docking ...

# Conflicts:
#	imgui.cpp