Merged from trunk 5247:5256

Merged from trunk 5247:5256

For bug #128809, process blockers for all installed packages.  Due to
the performance penalty incurred by additional dep_check calls, this is
only enabled with the --deep option.

Avoid unnecessary dbapi.cp_list() calls inside cpv_expand().

Cache the results of match_from_list() calls.

Cache results of dep_getcpv() calls.

Use dep_getcpv() inside dep_expand() for code sharing and caching.

Cache the results of fakedbapi.match() calls and clear the cache
automatically when necessary.

Initialize the match cache in the bindbapi constructor.

For bug #128809, optimize dep_check calls and enable the blocker
detection by default since the performance now seems acceptable.

Make sure the SLOT comes from the vardb instead of the portdb (for
multislot,   etc..). Thanks to jakub for reporting.

svn path=/main/branches/prefix/; revision=5259