glsl: support compilation of geometry shaders

glsl: support compilation of geometry shaders

This commit adds all of the parsing and semantics for GLSL 150 style
geometry shaders.

v2 (Paul Berry <stereotype441@gmail.com>): Add a few missing calls to
get_pipeline_stage().  Fix some signed/unsigned comparison warnings.
Fix handling of NULL consumer in assign_varying_locations().

v3 (Bryan Cain <bryancain3@gmail.com>): fix indexing order of 2D
arrays.  Also, allow interpolation qualifiers in geometry shaders.

v4 (Paul Berry <stereotype441@gmail.com>): Eliminate
get_pipeline_stage()--it is no longer needed thanks to 030ca23 (mesa:
renumber shader indices according to their placement in pipeline).
Remove 2D stuff.  Move vertices_per_prim() to ir.h, so that it will be
accessible from outside the linker.  Remove
inject_num_vertices_visitor.  Rework for GLSL 1.50.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
v5 (Paul Berry <stereotype441@gmail.com>): Split out
do_set_program_inouts() argument refactoring to a separate patch.
Move geom_array_resizing_visitor to later in the series.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>