swift234

When determining whether we can specialize a generic function,
check whether any of the substitutions are dependent rather
than checking whether the function's substituted type is
dependent.

This can't currently come up for user functions because Swift
doesn't permit type arguments to be given explicitly; hence a
dependent type argument will necessarily appear somewhere in
the substituted signature.  However, it's still possible in
the basic SIL model, and Joe's fix to default argument
initializers was just an obvious example.

Swift SVN r18768