Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_opengl3.cpp
#	imgui.cpp
#	imgui.h
#	imgui_draw.cpp
#	imgui_internal.h

Examples: OpenGL3: Added shaders more versions of GLSL + made the example app default to GL 3.0 + GLSL 130 (instead of GL 3.2 + GLSL 150) unless on Mac. (#1938, #1900, #1513, #1466, etc.)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Examples: Comments, Demo: Log early out, TODO. (#1553)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx10.h
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_glfw.cpp
#	examples/imgui_impl_glfw.h
#	examples/imgui_impl_opengl2.cpp
#	examples/imgui_impl_opengl2.h
#	examples/imgui_impl_opengl3.cpp
#	examples/imgui_impl_sdl.cpp
#	examples/imgui_impl_sdl.h
#	examples/imgui_impl_vulkan.h
#	examples/imgui_impl_win32.cpp

Comments, documentation

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp

Examples: Renamed imgui_impl_sdl2.cpp to imgui_impl_sdl.cpp (#1870) + changelog bits

Examples: Renamed example folders. (#1870)