WIP: move setup_attributes() to vs_vec4_visitor
WIP: move run() to vs_vec4_visitor
WIP: move emit_vertex_program_code() to vs_vec4_visitor
WIP: move setup_vp_regs() to vs_vec4_visitor
WIP: move get_vp_src_reg() to vs_vec4_visitor
WIP: move emit_attribute_fixups() to vs_vec4_visitor
WIP: move emit_urb_writes() to vs_vec4_visitor
WIP: move emit_urb_slot() to vs_vec4_visitor
WIP: move emit_generic_urb_slot() to vs_vec4_visitor
WIP: move emit_psiz_and_flags() to vs_vec4_visitor
WIP: move emit_clip_distances() to vs_vec4_visitor
WIP: move get_vp_dst_reg() to vs_vec4_visitor
WIP: move emit_ndc_computation() to vs_vec4_visitor
WIP: move c to vs_vec4_visitor.
WIP: move prog_data to vs_vec4_visitor
WIP: move vp_temp_regs to vs_vec4_visitor
WIP: move vp_addr_reg to vs_vec4_visitor