We were getting the wrong dynamic type if there were two classes with the same basename.

There's a bug in FindTypes, it ignores the exact flag if you pass a name that doesn't begin with
:: and pass eTypeClassAny for the type.

In this case we always know that the name we get from the vtable name is absolute so we can
work around the bug by prepending the "::".  This doesn't fix the FindTypes bug.

<rdar://problem/38010986>

llvm-svn: 326412