glsl/linker: Properly pack GS input varyings.

Since geometry shader inputs are arrays (where the array index
indicates which vertex is being examined), varying packing needs to
treat them differently.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/glsl/ir_optimization.h

@@ -112,7 +112,7 @@ bool lower_packing_builtins(exec_list *instructions, int op_mask);
 void lower_ubo_reference(struct gl_shader *shader, exec_list *instructions);
 void lower_packed_varyings(void *mem_ctx, unsigned location_base,
                            unsigned locations_used, ir_variable_mode mode,
-                           gl_shader *shader);
+                           unsigned gs_input_vertices, gl_shader *shader);
 bool lower_vector_insert(exec_list *instructions, bool lower_nonconstant_index);
 void lower_named_interface_blocks(void *mem_ctx, gl_shader *shader);
 bool optimize_redundant_jumps(exec_list *instructions);