posix: Clean up get_max_fds implementation.
* src/posix-io.c (get_max_fds): Return type is int. Ifdef-out TRACE. Remove call to sysconf. Use long for R and POS. Use aligned buffer for struct linux_dirent64.
- GnuPG-bug-id: T7694
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>