openmp: Handle non-static data members in allocate clause and other C++ allocate...

openmp: Handle non-static data members in allocate clause and other C++ allocate fixes

This allows specification of non-static data members in allocate clause like it
can be specified in other privatization clauses and adds a new testcase that covers
also handling of that clause in templates.

2020-10-30  Jakub Jelinek  <jakub@redhat.com>

	* semantics.c (finish_omp_clauses) <case OMP_CLAUSE_ALLOCATE>: Handle
	non-static members in methods.
	* pt.c (tsubst_omp_clauses): Handle OMP_CLAUSE_ALLOCATE.

	* c-c++-common/gomp/allocate-1.c (qux): Add another test.
	* g++.dg/gomp/allocate-1.C: New test.