testsuite_containers.h (forward_members_unordered<>::forward_members_unordered (const value_type&)): Add local_iterator pre and post increment checks.

2018-10-20  François Dumont  <fdumont@gcc.gnu.org>

	* testsuite/util/testsuite_containers.h
	(forward_members_unordered<>::forward_members_unordered
	(const value_type&)): Add local_iterator pre and post increment checks.
	* config/abi/pre/gnu.ver: Add GLIBCXX_3.4.26 new symbol.

From-SVN: r265344