add make delete-old and delete-old-libraries AND also needs mergemaster handling

[gustopn]

I ran into issues after upgrading because of old files that were still around.
Mainly it was the local_unbound renaming, however, this has to be taken care of.
Also mergemaster has to be ran somehow automatically.
But in a way that it does not remove group, master passwd and alike.

[gustopn]

Before doing mergemaster -iFU, it needs to backup all /etc/, best by rsync -aHAX into root dir backups (or somewhere where backups could go). If it does not want to use rsync (because that's a package that needs to be installed, it could also take TAR. However, then it gets harder to pick just one file by copying it over. That needs to be done by tar listing all files and then picking one to extract from the archive.
BTW: BATCH_DELETE_OLD_FILES does batch on delete-old and delete-old-libraries.

[gustopn]

for jails it is not worth the time to run mergemaster interactively. It makes more sense to just overwrite it all with make distribution, let mergemaster -iFU remove all unneeded files and then roll back the files which we need, like master.passwd and ssh config and alike. Do not forget to run pwd_mkdb.

[gustopn]

One example:
for i injls -N name; do if [ -d /jail/$i ]; then export DESTDIR="/jail/$i"; make -DBATCH_DELETE_OLD_FILES delete-old; make -DBATCH_DELETE_OLD_FILES delete-old-libs; fi; done