[MS-ABI] Update to alias-avoidance padding
This patch changes how we determine if padding is needed between two 
bases in msvc compatibility mode.  Test cases included.

In addition, a very minor change to the printing of structures to ease 
lit testing.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@205933 91177308-0d34-0410-b5e6-96231b3b80d8