When creating a call to a base subobject's operator= in an

When creating a call to a base subobject's operator= in an
implicitly-defined copy assignment operator, suppress the protected
access check. This eliminates the remaining failure in the
Boost.SmartPtr library (that was a product of the copy-assignment
generation rewrite) and, presumably, the Boost.TR1 library as well.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@103010 91177308-0d34-0410-b5e6-96231b3b80d8