When a filesystem package with usrmerge is detected (/bin, /sbin, /lib
or /lib64 link to /usr), pretend all files in the affected dirs are
actually in /usr.
The file names are generated out of the sha1sum of the file content. Thus we
know if the file has the same name, it has the same content as well. Multiple
packages are allowed to own the same file with the same content. This is already
proven functional by the kernel being flavor:multiversion - the kernel can
be installed in multiple versions already (which the checked never would have
caught file conflicts for: we only check against current packages in the distro)
Fixes issue #2350
Extract the writing of the susetags content into a new script that
also creates a yaml file which package comes from what directory.
This information is used in repochecks.py to run findfileconflicts
and installcheck as repo_checker.pl used to
