glsl: convert GS input primitive to use ast_type_qualifier

glsl: convert GS input primitive to use ast_type_qualifier

We introduce a new merge_in_qualifier ast_type_qualifier
which allows specialized handling of merging input layout
qualifiers.

By merging layout qualifiers into state->in_qualifier, we
allow multiple input qualifiers. For example, the primitive
type can be specified specified separately from the
invocations count (ARB_gpu_shader5).

state->gs_input_prim_type is moved into state->in_qualifier->prim_type

state->gs_input_prim_type_specified is still processed separately
so we can determine when the input primitive is specified. This
is important since certain scenerios are not supported until after
the primitive type has been specified in the shader code.

v4:
 * Merge with compute shader input layout qualifiers

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>