Change ref count logic in halide_release to take into account that the command queue holds a reference to the context.
Change ref count logic in halide_release to take into account
that the command queue holds a reference to the context.

Add extra debug output to copy_to_host to print buf ptr.


Former-commit-id: 2602fc8cbf93a471def3a9a0eeb93805af46e404
Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide