Implement "sin" and "cos" builtins via new expression operators.

ir.cpp

@@ -73,6 +73,9 @@ ir_expression::get_num_operands(ir_expression_operation op)
       1, /* ir_unop_ceil */
       1, /* ir_unop_floor */
 
+      1, /* ir_unop_sin */
+      1, /* ir_unop_cos */
+
       2, /* ir_binop_add */
       2, /* ir_binop_sub */
       2, /* ir_binop_mul */
@@ -131,6 +134,8 @@ static const char *const operator_strs[] = {
    "trunc",
    "ceil",
    "floor",
+   "sin",
+   "cos",
    "+",
    "-",
    "*",