Examples: Comments + shallow coding convention tweak to be consistent across examples and with imgui_impl_osx

Examples: Removed old example_apple/ + tweak comments (#1873)

Merge branch 'warrenm_osx'

Apple: Fixed example_osx_opengl2, renamed to example_apple_opengl2 + misc comments

Allow popup from ignoring the style.WindowMinSize values so short menus are not padded. (#1909) Wider generalization of b166037.

Internals: Removed unused ShadeVertsLinearAlphaGradientForLeftToRightText code.

Removed per-window ImGuiWindowFlags_ResizeFromAnySide beta flag in favor `io.OptResizeWindowsFromEdges=true` to enable the feature globally. (#1495) The feature is not currently enabled by default because it is not satisfying enough.

Introduced a new Metal renderer implementation and a new example illustrating usage of Metal on macOS and iOS (partially addresses #1873)

Internals: BeginChildEx tweaks.

Examples: Comments, bits of documentation

OSX: Various tweaks to imgui_impl_osx courtesy of @warrenm + fix NewFrame position which has been moved recently master. (#1873)

Merge branch 'master' into osx ...

# Conflicts:
#	examples/.gitignore
#	examples/README.txt

Links and thanks. Comments on using BeginCombo/EndCombo + moved the Combo() implementations closer to each others to maximize user seeing how it is implemented from any of the secondary function body.

Ignore list: added emscripten output

Examples: Ignore all *.user files (#1919) ...

For example `Qt Creator` create `CMakeLists.txt.user` file with user settings.

Fixed a include build issue for Cygwin in non-POSIX (Win32) mode. (#1917, #1319, #276)

Examples: Comments to clarify how the keyboard data is indexed.

Fix include Example_glfw_vulkan cmake (#1916) ...

Probably got broken because of the refactor.

Tweaked software mouse cursor offset to match the offset of the corresponding Windows 10 cursors. (followup to #1914)

Fixed software Hand cursor from not actually working. Fixed demo from crashing. Fixed typo and extraneous trailing space. Added Changelogs. (#1913, #1914)

add hand cursor support (+11 squashed commit)

Internals: Settings: Simple optimization caching index into the settings buffer, to remove an unnecessary O(N*M) search during saving. (with N=active root windows during the session, M=stored settings which grows over time)

ImVector: Added index_from_pointer() helper.

Allow menu windows from ignoring the style.WindowMinSize values so short menus are not padded. (#1909)

Double-click on resize grip doesn't need to test HoveredWindow (as button has the flattenchild flag anyway) + double-click on title bar verify that we don't have overlapping items to allow contents in title bar. + Comments

Examples: Apple: Fixed paths of GLFW+GL2 example. (#1906) Update ignore list.

Internals: Various renaming. e.g. NewFrameUpdateHoveredWindowAndCaptureFlags() to UpdateHoveredWindowAndCaptureFlags() + exposed UpdateMovingWindow() in imgui_internal.h.

ArrowButton: Fixed to honor PushButtonRepeat() setting (and internals' ImGuiItemFlags_ButtonRepeat). Setup current line text baseline so that ArrowButton() + SameLine() + Text() are aligned properly.

Internals: Moved some of the SliderBehaviorT code into SliderBehavior to reduce the amount of instanciated code.

Examples: OpenGL3: Remove misleading or unnecessary "#version 150" strings.