Also use a simple `seen' cache for files only used by one package, since
they cannot participate in actual conflicts.
Shrinks memory for 250M to 190M, with no negative speed effects.
use auto-vivification to shorten code a bit.
pull out complicated code into its own function.
marginally faster than old version... some size decrease to do later...
without the need to have the packages around.
It's really easy now to check if a new package conflicts with other stuff
in the ports-tree:
$ find-all-conflicts -p /usr/ports newpkg.tgz
help & ok espie@
any level in the dependency tree, but we shouldn't mark as conflicting packages
that do depend on each other or that have common dependencies.
Issue noticed by alek@ on plone vs. zope.
