swift234

progress towards non-member observing properties:
 - Add a "isDirectPropertyAccess" bit to DeclRefExpr, serving the 
   same purpose as MemberRefExprs for non-member properties.
 - Teach sema to synthesize correct non-member get/set implementations
   for observing properties.
 - Teach silgen to handle the isDirectPropertyAccess bit.



Swift SVN r13600