Apple: Fixed example_osx_opengl2, renamed to example_apple_opengl2 + misc comments

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

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

Ignore list: added emscripten output

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

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

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

Fix include Example_glfw_vulkan cmake (#1916) ...

Probably got broken because of the refactor.

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)

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

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

Examples: Fixes.

Examples: Vulkan: nverted the parameters to ImGui_ImplVulkan_RenderDrawData() to be consistent with other bindings.

Examples: DirectX12: Moved the ID3D12GraphicsCommandList* parameter from ImGui_ImplDX12_NewFrame() to ImGui_ImplDX12_RenderDrawData() which makes a lots more sense. (#301)

Examples: The functions in imgui_impl_xxx.cpp are prefixed with IMGUI_IMPL_API (which defaults to IMGUI_API) to facilitate some uses. (#1888) + Comments in imgui.h

Examples: SDL+OpenGL2: Fixed Makefile. (#1886)

Examples: Fixed bindings to use ImGuiMouseCursor_COUNT instead of old name ImGuiMouseCursor_Count_ so they can compile with IMGUI_DISABLE_OBSOLETE_FUNCTIONS. (#1887)

Readme, Links, Bindings

Fixed warnings + readme

Examples: OSX: Added clipboard support. Fixed ignore list for xcode cruft. Comments about broken keys. (#1873)

Examples: Allegro5: Added support for ImGuiConfigFlags_NoMouseCursorChange flag. Added clipboard support. Unindexing buffers ourselves as Allegro indexed drawing primitives are buggy in the DirectX9 back-end.

Internals: Added GetItemID(), GetFocusID() for consistency. Made GetActiveID() inline. Comments, fixed typos, demo tweaks.

Examples: OSX: Fixed obsolete enums. Fixed keyboard mapping. Added missing keyboard modifiers. (#1873)

Examples: FreeGLUT: Fixed mapping of Space key. (#801)

Comments, documentation

Examples: FreeGLUT: Added FreeGLUT bindings. Added FreeGLUT+OpenGL2 example. (#801)

Examples: Win32: Fixed handling of mouse wheel messages to support finer position messages (typically sent by track-pads). (#1874)

Examples: Comments to make ImGuiConfigFlags_NoMouseCursorChange more visible (#1027). + Allegro5: Added support for ImGuiConfigFlags_NoMouseCursorChange flag.