It does not matter what we actually do, just make sure we don't crash -- we did
not have tests for bitfields previously. Related: rdar://15671755
Swift SVN r11363
This change moves the swift overlay modules from Clang importer mock sdk to a
central location. (Otherwise we try to deserialize the Foundation overlay for
the system framework, and crash because we don't find all declarations in
our mock sdk.)
Swift SVN r11297