Added tests for integer division.
Added tests for integer division.

Also removed tests that relied on us being able to represent
int32s internally.


Former-commit-id: a4db9dd62f6aead4749f5f70233f710709aceec7
darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide