openmp: Ensure DECL_CONTEXT of OpenMP iterators in templates [PR105092]

openmp: Ensure DECL_CONTEXT of OpenMP iterators in templates [PR105092]

cp_parser_omp_iterators does:
      DECL_ARTIFICIAL (iter_var) = 1;
      DECL_CONTEXT (iter_var) = current_function_decl;
      pushdecl (iter_var);
on the newly created iterator vars, but when we instantiate templates
containing them, we just tsubst_decl them (which apparently for
automatic vars clears DECL_CONTEXT with a comment that pushdecl should
be called on them later).
The result is that we have automatic vars in the IL which have NULL
DECL_CONTEXT and the analyzer is upset about those.

Fixed by setting DECL_CONTEXT and calling pushdecl during the instantiation.

2022-03-30  Jakub Jelinek  <jakub@redhat.com>

	PR c++/105092
	* pt.cc (tsubst_omp_clause_decl): When handling iterators, set
	DECL_CONTEXT of the iterator var to current_function_decl and
	call pushdecl.

	* g++.dg/gomp/pr105092.C: New test.