[OPENMP 4.5] Ccapture/codegen of private non-static data members.

[OPENMP 4.5] Ccapture/codegen of private non-static data members.
OpenMP 4.5 introduces privatization of non-static data members of current class in non-static member functions.
To correctly handle such kind of privatization a new (pseudo)declaration VarDecl-based node is added. It allows to reuse an existing code for capturing variables in Lambdas/Block/Captured blocks of code for correct privatization and codegen.

llvm-svn: 260077