Added some helpful new IR operators for min, max, clamp, and cast
Added some helpful new IR operators for min, max, clamp, and cast


Former-commit-id: ca67633c02e74fd71f144bc68dd5b7b44b1b5611
darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide