Merge branch 'master' into viewport

# Conflicts:
#	examples/imgui_impl_opengl3.cpp
#	imgui.cpp

examples/imgui_impl_opengl3.h

@@ -10,6 +10,11 @@
 // If you are new to dear imgui, read examples/README.txt and read the documentation at the top of imgui.cpp.
 // https://github.com/ocornut/imgui
 
+// About OpenGL function loaders:
+// Modern OpenGL requires individual functions to be loaded manually. Helper libraries are often used for this purpose.
+// Here we are using gl3w.h, which requires a call to gl3wInit(). 
+// You may use another any other loader/header of your choice, such as glew, glext, glad, glLoadGen, etc.
+
 // About GLSL version:
 // The 'glsl_version' initialization parameter defaults to "#version 130" if NULL.
 // Only override if your GL version doesn't handle this GLSL version (see table at the top of imgui_impl_opengl3.cpp). Keep NULL if unsure!