Prefix more error messages with GLSL to make clear where they are coming from
Use negative values to signal errors in OpenGL context creation
Add minimal test for OpenGL float textures
Generate correct GLSL code for float textures
Minor cleanup
Correctly transfer floating point textures on GL and GL ES

Turns out this is one of the places where the desktop and mobile versions of
OpenGL use slightly different conventions that yield significantly different
results...
Merge branch 'master' into glsl_float_textures
Use Halide conventions for enums

CamelCase instead of UPPERCASE
Add support for running with OpenGL 3.2 core profile

Right now, the runtime doesn't work with older OpenGL and ES anymore, so
there's some backporting work still to be done...
Merge branch 'master' into glsl_float_textures
Better handling of optional OpenGL functionality

texture_rg: textures with just one or two channels
vertex_array_object: required for OpenGL >= 3.0
Create OpenGL 3.2 Core context on Linux

This is mainly to ensure that Halide works correctly with modern OpenGL, in
particular in applications that don't provide compatibility contexts.
Merge branch 'master' into glsl_float_textures

Conflicts:
	src/CodeGen_OpenGL_Dev.cpp
	src/runtime/opengl.cpp
Merge branch 'master' into glsl_float_textures

Conflicts:
	src/runtime/opengl.cpp
Merge branch 'master' into glsl_float_textures
Merge remote-tracking branch 'origin/no_varargs' into glsl_float_textures

Conflicts:
	src/runtime/opengl.cpp
	test/scripts/distrib_windows.ps1
Use new runtime I/O functions
Query OpenGL extensions to look for supported features

Right now, this is only done for texture_rg, but in the future the same
mechanism can be used for things like float textures, integer arithmetic,
compute shaders, ...
Test for availability of floating point textures
Fix the print test on windows