Load program binary extension on Linux
Fix rebase
Merge pull request #698 from mapbox/cache-shaders

Add caching of compiled shaders
Merge branch 'master' of github.com:mapbox/mapbox-gl-native into android-mason

Conflicts:
	include/mbgl/platform/gl.hpp
	src/mbgl/platform/gl.cpp
	src/mbgl/shader/shader.cpp
Add pakced depth stencil to GLFWView and HeadlessView