Move mount related functions into libmount

[dim]

Summary

This avoids several programs using .PATH to reach over into the
sbin/mount subdirectory to recompile getmntopts.c, mounttab.c or
vfslist.c, namely:

• sbin/fsck
• sbin/fsck_ffs
• sbin/growfs
• sbin/init
• sbin/mksnap_ffs
• sbin/mount_cd9660
• sbin/mount_fusefs
• sbin/mount_msdosfs
• sbin/mount_nfs
• sbin/mount_nullfs
• sbin/mount_udf
• sbin/mount_unionfs
• sbin/tunefs
• sbin/umount
• tests/sys/fs/fusefs
• usr.sbin/autofs
• usr.sbin/mount_smbfs
• usr.sbin/mountd
• usr.sbin/rpc.umntall

MFC after: 1 week

[brooks]

Sorry, I should have added you to D49951 and D49952 which this duplicates. I don't think a new library is warranted and if it is, it should probably be libmntopts or the like not something as generic as libmount.

I've commented on one makefile with some complaints that apply to most of them.

usr.sbin/mountd/Makefile

2

This line is now is gratuitous (SRCS=${PROG}.c by default)

5

The installed copy should be used.