glsl: Apply memory qualifiers to buffer variables

glsl: Apply memory qualifiers to buffer variables

v2:
  - Save memory qualifier info in the top level members of a shader
    storage block.
  - Add a checks to record_compare() which is used when comparing
    shader storage buffer declarations in different shaders.
  - Always report an error for incompatible readonly/writeonly
    definitions, whether they are present at block or field level.

Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>