glsl: Evaluate constant pack/unpack 4x8 expressions

That is, evaluate constant expressions for the following functions:
  packSnorm4x8, unpackSnorm4x8
  packUnorm4x8, unpackUnorm4x8

Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>
1 file changed