More work on constructors. Basic testcases with "constructor" declarations appear to be working, although there's probably more work to be done. (Both old-style and new-style constructors work for the moment.)

Swift SVN r2163

lib/AST/Module.cpp

@@ -392,6 +392,9 @@ void Module::lookupValueConstructors(Type BaseType,
     return;
   }
 
+  DoGlobalExtensionLookup(BaseType, Name, BaseMembers, this, cast<Module>(DC),
+                          Result);
+  Name = Ctx.getIdentifier("constructor");
   DoGlobalExtensionLookup(BaseType, Name, BaseMembers, this, cast<Module>(DC),
                           Result);
 }