glsl: Don't use random pointers as an array of glsl_type objects.

glsl: Don't use random pointers as an array of glsl_type objects.

Using a random glsl_type convenience pointer as an array is a really bad
idea, for all the reasons mentioned in the previous commit.

The new glsl_type::bvec() function is simpler anyway.

Prevents breakage in the next commit.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>