[IMPROVED] The behavior with union file systems is stabilized.

[IMPROVED] The behavior with union file systems is stabilized.

	modified:   Makefile
	modified:   bin/portsreinstall
	modified:   bin/portsreinstall-chroot
	modified:   lib/chroot-mount/libmain.sh
	modified:   lib/chroot/libfs.sh
	modified:   lib/chroot/libmain.sh
	modified:   lib/chroot/liboptions.sh
	modified:   lib/libconf.sh
	modified:   lib/libdatabase_build.sh
	modified:   lib/libdatabase_record.sh
	modified:   lib/libdeinstall.sh
	new file:   lib/libfs.sh
	modified:   lib/libmain.sh
	modified:   lib/libmisc.sh
	modified:   lib/libpkgsys.sh
	modified:   lib/libreinstall.sh
	modified:   lib/upgrade/liboptions.sh
	modified:   man/portsreinstall.8
	modified:   share/bin/portsreinstall-chroot-mount
	modified:   share/bin/portsreinstall-upgrade