glsl: Add ir_unop_sin_reduced and ir_unop_cos_reduced

The operate just like ir_unop_sin and ir_unop_cos except that they
expect their inputs to be limited to the range [-pi, pi].  Several
GPUs require this limited range for their sine and cosine
instructions, so having these as operations (along with a to-be-written
lowering pass) helps this architectures.

These new operations also matche the semantics of the
GL_ARB_fragment_program SCS instruction.  Having these as operations
helps in generating GLSL IR directly from assembly fragment programs.

src/glsl/ir_validate.cpp

@@ -273,6 +273,8 @@ ir_validate::visit_leave(ir_expression *ir)
    case ir_unop_fract:
    case ir_unop_sin:
    case ir_unop_cos:
+   case ir_unop_sin_reduced:
+   case ir_unop_cos_reduced:
    case ir_unop_dFdx:
    case ir_unop_dFdy:
       assert(ir->operands[0]->type->base_type == GLSL_TYPE_FLOAT);