swift234

Properly compute the override set for accessors in subscripts 
and properties, allowing us to set up vtables properly.  Before
this patch, we'd get new entries in the derived class vtable for
overridden property accessors, which didn't help things.

This is progress along the way towards fixing:
<rdar://problem/16310561> Property vtables not set up correctly
but isn't the full story.  Dispatch is still not going through the vtable,
so we get the wrong behavior still.


This patch also exposes a totally mystifying (to me) problem with the deserializer.
A test is temporarily disabled because of this.




Swift SVN r15051