Refine vtable, rtti and rtti name instantiation so that they follow

Refine vtable, rtti and rtti name instantiation so that they follow
the key function.  All the code is wired up, but won't work yet, as I
had to turn off key function calculation as it doesn't work yet.

Also, we refine visibility of the vtable, rtti and rtti name to match
the class, as well as as arrange for all the symbols to be internal
for anonymous namespace entities.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@89309 91177308-0d34-0410-b5e6-96231b3b80d8