Structs starting with `r' in bsd/kern

• read_args bsd/kern/sys_generic.c:90
• readv_args bsd/kern/sys_generic.c:112
• reboot_args bsd/kern/kern_xxx.c:186
• recvfrom_args bsd/kern/uipc_syscalls.c:701
• recvmsg_args bsd/kern/uipc_syscalls.c:833