[APINotes] Use non-"Ref" names for CG import-as-member renamings.

That is, import something like 'CGColorCreateGenericGray' as
"CGColor.init(gray:alpha:)" rather than "CGColorRef.init(gray:alpha:)".
Since we print the type name in diagnostic text and in fix-its, it's
important to use the name that Swift sources use.

Finishes rdar://problem/26347297.

Author: jrose-apple