Most tests were using %swift or similar substitutions, which did not
include the target triple and SDK. The driver was defaulting to the
host OS. Thus, we could not run the tests when the standard library was
not built for OS X.
Swift SVN r24504
This includes proper rules for function overloads (i.e. shadowing by type)
and allowing type lookup to find a type even if it has the same name as
a non-type.
lookupVisibleDecls does not use this behavior yet.
Swift SVN r7016
