Structs starting with `r' in osfmk/mach

• region_desc osfmk/mach/boot_info.h:139
• request_block osfmk/mach/kkt_request.h:301
• routine_arg_descriptor osfmk/mach/rpc.h:180
• routine_descriptor osfmk/mach/rpc.h:188
• rpc_copy_state osfmk/mach/rpc.h:362
• rpc_signature osfmk/mach/rpc.h:203
• rpc_subsystem osfmk/mach/rpc.h:233