glsl: Add an option to clamp block indices when lowering UBO/SSBOs

This prevents array overflow when the block is actually an array of UBOs or
SSBOs.  On some hardware such as i965, such overflows can cause GPU hangs.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/glsl/ir_optimization.h

@@ -123,7 +123,7 @@ bool lower_clip_cull_distance(struct gl_shader_program *prog, gl_shader *shader)
 void lower_output_reads(unsigned stage, exec_list *instructions);
 bool lower_packing_builtins(exec_list *instructions, int op_mask);
 void lower_shared_reference(struct gl_shader *shader, unsigned *shared_size);
-void lower_ubo_reference(struct gl_shader *shader);
+void lower_ubo_reference(struct gl_shader *shader, bool clamp_block_indices);
 void lower_packed_varyings(void *mem_ctx,
                            unsigned locations_used, ir_variable_mode mode,
                            unsigned gs_input_vertices, gl_shader *shader,