Without this, we try to bring these in as CF types, and then ARC tries to
manage them, and the program crashes.
<rdar://problem/17211521>
Swift SVN r21081
This is a step towards making the framework easier to use in Swift; in the
actual headers, these are typed as "CFTypeRef" or "const CFTypeRef", which
is not considered Hashable (and thus cannot be put in a dictionary).
Unfortunately, CFStringRef is also not hashable, so we're not there yet,
but at least this allows a freer conversion to NSString.
Part of <rdar://problem/17162475>
Swift SVN r20931
