- Move uid16 functions to their own file linux_uid16.c, included by
needed archs (arm, i386 and m68k).
- Add new MI types linux_{u,g}id16_t.
- Add macros to handle linux_uid16_t and uid_t conversions.
- Add linux_sys_getres{uid,gid}16 syscalls, to fix an overflow with
bad sizes given to copyout when linux_sys_getres{uid,gid} are used.
- Update arm syscall table to use more uid16 functions.