Initial ptx (CUDA) math library support. Not tested yet.
Add support for math library functions on PTX target (CUDA) via
NVidia's libdevice mechanism.
Merge branch 'master' into ptx_math
Disable ptx backend on llvm 3.2
Add missing include.
Merge branch 'master' into ptx_math

Conflicts:
	src/Target.cpp
Fix totally incorrect generation of abs_ intrinsic calls
Merge branch 'master' of github.com:halide/Halide