Implement debug info for willset/didset, and teach dispatch to be non-virtual

to didset/will set since we don't drop these in the class vtable.


Swift SVN r13056

lib/IRGen/GenProto.cpp

@@ -243,7 +243,7 @@ namespace {
     }
 
     void visitFunc(FuncDecl *func) {
-      if (func->isGetterOrSetter())
+      if (func->isAccessor())
         // FIXME: To be implemented.
         return;