* sysdeps/m68k/bits/byteswap.h: Allow inclusion from <endian.h>.
(__bswap_constant_16): Define.
(__bswap_16): Allow arguments with side effects.
(__bswap_constant_32): Ensure result is unsigned.
(__bswap_32): Define as inline function in fallback case.
(__bswap_constant_64): Define.
(__bswap_64): Use it for constant arguments.
* sysdeps/m68k/bits/setjmp.h (__jmp_buf): Give name to structure
type.
* sysdeps/m68k/m680x0/fpu/bits/mathinline.h: Only allow inclusion
from <math.h>. Do not use extern inline directly.
* sysdeps/unix/sysv/linux/m68k/bits/fcntl.h: Include <bits/uio.h>.
(O_CLOEXEC, SYNC_FILE_RANGE_WAIT_BEFORE, SYNC_FILE_RANGE_WRITE,
SYNC_FILE_RANGE_WAIT_AFTER, SPLICE_F_MOVE, SPLICE_F_NONBLOCK,
SPLICE_F_MORE, SPLICE_F_GIFT): Define.
(sync_file_range, vmsplice, splice, tee): Declare.
* sysdeps/unix/sysv/linux/m68k/bits/mman.h (MADV_REMOVE): Define.
* sysdeps/unix/sysv/linux/m68k/bits/poll.h (POLLMSG, POLLREMOVE,
POLLRDHUP): Define.
* sysdeps/unix/sysv/linux/m68k/bits/stat.h (UTIME_NOW,
UTIME_OMIT): Define.
* sysdeps/unix/sysv/linux/m68k/kernel-features.h: New.
* sysdeps/unix/sysv/linux/m68k/sys/user.h: New.
