[OPENMP 4.5] Initial support for data members in 'lastprivate' clause.

OpenMP 4.5 allows to privatize non-static data members of current class
in non-static member functions. Patch adds initial support for data
members.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@261412 91177308-0d34-0410-b5e6-96231b3b80d8