swift234

Convert PrintAsObjC over to conformance lookup table entrypoints.

Another step toward using the conformance lookup table for
everything. This uncovered a tricky little bug in the conformance
lookup table's filtering logic (when asking for only those
conformances explicitly specified within a particular context) that
would end up dropping non-explicit conformances from the table (rather
than just the result).

Ween a few tests off of -enable-source-import, because they'll break
otherwise.

Swift SVN r27021