Itanium ABI: Update getAddrOfVTable to set the DLL storage class for vtables

This corresponds to the same change for the MS ABI in r209908.

Differential Revision: http://reviews.llvm.org/D3993

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@210054 91177308-0d34-0410-b5e6-96231b3b80d8