nilfs-utils: do not use C99 style comments

This fixes the following checkpatch errors:

 ERROR: do not use C99 // comments
 #1711: FILE: sbin/mkfs/mkfs.c:1711:
 +       //commit_ifile();

 ERROR: do not use C99 // comments
 #1714: FILE: sbin/mkfs/mkfs.c:1714:
 +       //commit_dat();

 ERROR: do not use C99 // comments
 #37: FILE: sbin/mount/sundries.c:37:
 +//#include "nfsmount.h"

 ERROR: do not use C99 // comments
 #485: FILE: sbin/mount/umount.nilfs2.c:485:
 +// writemtab:

 ERROR: do not use C99 // comments
 #86: FILE: include/nilfs.h:86:
 +typedef __u64 sector_t;        // XXX: __u64 ??

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
nilfs-utils: use tabs where possible for code indent

This fixes the following checkpatch error:

 ERROR: code indent should use tabs where possible
 #46: FILE: sbin/mkfs/mkfs.h:46:
 +^I^I^I^I^I        (non-reserved) segments */$

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>