tree-optimization/115232 - demangle failure during -Waccess

tree-optimization/115232 - demangle failure during -Waccess

For the following testcase we fail to demangle
_ZZN5OuterIvE6methodIvEEvvQ3cstITL0__EEN5InnernwEm and
_ZZN5OuterIvE6methodIvEEvvQ3cstITL0__EEN5InnerdlEPv and in turn end
up building NULL references.  The following puts in a safeguard for
faile demangling into -Waccess.

	PR tree-optimization/115232
	* gimple-ssa-warn-access.cc (new_delete_mismatch_p): Handle
	failure to demangle gracefully.

	* g++.dg/pr115232.C: New testcase.