x32: update io_{setup,submit} syscalls

Starting in 3.16, these two syscalls have gotten their own entry
point for x32.  See linux 7fd44dacdd803c0bbf38bf478d51d280902bb0f1.

* linux/x32/syscallent.h: Change existing io_{setup,submit} to 64bit,
and add new entry points for x32 specifically.
Decode file descriptors returned by accept and accept4 syscalls

* net.c (do_accept): Rename to do_sockname.
(sys_accept, sys_accept4): Update callers, return RVAL_FD.
(sys_getsockname, sys_getpeername): Call do_sockname directly.
* tests/net-fd.test: Update.
Fix preadv/pwritev offset decoding on bigendian architectures

This partially reverts commit 7845a42b39e59e904d01e75e21f7bc7eb6462560.

* util.c (printllval): Remove align argument.
* defs.h (printllval): Update prototype.
(printllval_aligned, printllval_unaligned): Remove.
* file.c (sys_readahead, sys_truncate64, sys_ftruncate64, sys_fadvise64,
sys_fadvise64_64, sys_sync_file_range, sys_sync_file_range2,
sys_fallocate): Replace printllval_aligned call with printllval.
* io.c (sys_pread, sys_pwrite): Likewise.
(print_llu_from_low_high_val): New function.
(sys_preadv, sys_pwritev): Use it instead of printllval_unaligned.
Fix preadv/pwritev offset decoding on ILP32 architectures

This fixes regression introduced by the previous commit.

* io.c (print_llu_from_low_high_val) [SIZEOF_LONG != SIZEOF_LONG_LONG]:
Cast argument to unsigned long before casting it to unsigned long long.