Update HelloAndroid for more recent Android SDK
Added small sample app for testing OpenGL functionality on Android
Changes to OpenGL backend to enable basic functionality on Android
Merge branch 'master' into opengl-android
Removed unused files
Fix name mangling for GLSL

Identifiers containing "__" *anywhere* are reserved in GLSL. Turns out that
Android's OpenGL implementation enforces this...
Store GLSL kernels in module state, as other GPU backends do
Handle repeated calls to halide_dev_malloc correctly
Started GLES-based Android App that shares context w/Halide

Missing things:
- pass textures to native Halide code
- call Halide filter
- adjust shaders in UI to actually display filtered texture
- use a more interesting Halide filter
GLSL doesn't know ?:, use if instead
Small improvements to OpenGL runtime
Don't convert Extern calls to GLSL intrinsics
Finish OpenGL-based test app
Rename OpenGL demo to avoid name clashes
Merge branch 'master' into opengl-android
Revert unintended changes to HelloAndroid example
Cleanup halide_opengl_create_context
Make halide_printf output to LOG_INFO, not LOG_FATAL
Move OpenGL context creation to android_opengl_context.cpp
Merge branch 'master' into opengl-android

Conflicts:
	Makefile
	src/runtime/android_io.cpp
	src/runtime/opengl.cpp