Speed up PROVIDED-SYSTEMS and PROVIDED-RELEASES for dists.
Speed up PROVIDED-SYSTEMS and PROVIDED-RELEASES for dists.

Going to the CDB for a single entry is way faster than initializing
the whole index and then checking for that entry. But it's way slower
to build up a list of *all* entries from the CDB. So use the plain
text files to initialize a slot for PROVIDED-SYSTEMS and
PROVIDED-RELEASES.

CodyReichert/quicklisp-client,daewok/quicklisp-client,PuercoPop/quicklisp-client,arnoo/quicklisp-client,tamurashingo/quicklisp-client,quicklisp/quicklisp-client