Fix insidious RegionStore bug where we (a) didn't handle vector types and (b) had

a horrible bug in GetLazyBindings where we falsely appended a field suffix when traversing 3 or more
layers of lazy bindings.  I don't have a reduced test case yet; but I have added the original source
to an internal regression test suite.  I'll see about coming up with a reduced test case.

Fixes <rdar://problem/11405978> (for real).

llvm-svn: 156580