hashtable.h (_Hashtable<>::__rehash_policy(const _RehashPolicy&)): Commit the modification of the policy only if no exception occured.

2011-09-17  François Dumont  <fdumont@gcc.gnu.org>

	* include/bits/hashtable.h (_Hashtable<>::__rehash_policy(const
	_RehashPolicy&)): Commit the modification of the policy only if no
	exception occured.
	* testsuite/23_containers/unordered_set/max_load_factor/robustness.cc:
	New.

From-SVN: r178927