Correctly check for distructors when realizing vtordisps

This patch fixes the distructor test when checking for vtordisp requirements in 
microsoft record layout.  A test case is also included.

Addresses:
http://llvm.org/bugs/show_bug.cgi?id=16406#c7



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192616 91177308-0d34-0410-b5e6-96231b3b80d8