If a buffer is not written to and is accessed uniformly w.r.t. thread indices, put it in constant memory.
Merge branch 'master' into gpu_constant_memory
Moved GPU constant memory queries to CodeGen_GPU_Dev
Added size of static images to buffers captured in a closure.
Generated kernel code build options.
Added GPU_Argument which passes the known size of buffers to the GPU device code generators, implemented constant memory more robustly for OpenCL C.
Merge branch 'master' into gpu_constant_memory
Replaced std::pair with struct.
Fixed address spaces for __constant buffers.
Added test that uses a constant generated Func (should map to constant memory in GPU targets).
Added tests for generated and multiple constant funcs in GPU pipelines.
Merge branch 'gpu_constant_memory' of https://github.com/halide/Halide into gpu_constant_memory

Conflicts:
	test/correctness/convolution_generated_kernel.cpp
Fixed tabs -> spaces.
Added operator < to BufferSize, removed equivalent functor predicate.
Cleaned up tests for constant memory buffers.
Fixed computation of the size of an image buffer.
Fixed potential bugs caused by not visiting Store index subexpressions.
Fix input image path in lesson 7
Add -lpthread -ldl back to suggested compile line for tutorials.
Make shared opencl memory an int16 instead of a ulong

ulong crashed the adreno drivers on my nexus 5