Assume that F_SETLK64, F_SETLKW64, and F_GETLK64 are either defined or
not defined altogether.
Do not assume that sizeof(off_t) < sizeof(long long) when F_SETLK64 is
This change fixes build with musl libc on x86.
* configure.ac: Define SIZEOF_OFF_T.
* desc.c (USE_PRINTFLOCK64): New macro.
(struct flock64, printflock64): Do not define on X32.
(printflock): Replace X32 specific workaround with SIZEOF_OFF_T check.
Fix printing off_t members of struct flock.
(sys_fcntl): Use USE_PRINTFLOCK64.