Defines starting with `m' in kern

• MAX_COMP_T_FRACT kern/kern_acct.c:103
• MAXLKMS kern/kern_lkm.c:76
• MAX_SPEED kern/tty_compat.c:57
• MBTYPES kern/uipc_mbuf.c:40
• MSG_COMPAT kern/uipc_syscalls.c:430