swift234

Design and implement the [byref] attribute, checking that
it doesn't appear in places it shouldn't.  The only limits on
this checking right now is the inadequacy of location information
for types, which is something we ought to fix.

Fix type-checking of byref applications.  Fix IR generation
of byref variables.  Whole lotta fixin' goin' on.

But hey, byref calls work.



Swift SVN r1111