Added ability to make static assertions about inputs
Added ability to make static assertions about inputs

You can now tell Halide the size and stride of ImageParams. If
the promises are violated at runtime, an error is raised.


Former-commit-id: e6dc8cc120f2c78b14718e99932d0739c8ea7f44
darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide