glsl_type: Don't have two versions of a type with the same name

Previously some sampler types were duplicated in GLSL 1.30 and
GL_EXT_texture_array.  This resulted in not being able to find the
built-in sampler functions when the extension was used.  When the
built-in functions were compiled, they bound to the 1.30 version.
This caused a type mismatch when trying to find the function.  It also
resulted in a confusing error message:

0:0(0): error: no matching function for call to `texture2DArray(sampler2DArray, vec3)'
0:0(0): error: candidates are: vec4 texture2DArray(sampler2DArray, vec3)

0:0(0): error:                 vec4 texture2DArray(sampler2DArray, vec3, float)

0 files changed, 0 insertions, 0 deletions