uclibc++: patch bugfix erase() on derived __base_associative

When calling erase() on a containers derived from __base_associative
(e.g. multimap) and providing a pair of iterators a segfault will
occur.

Example code to reproduce:

	typedef std::multimap<int, int> testmap;
	testmap t;
	t.insert(std::pair<int, int>(1, 1));
	t.insert(std::pair<int, int>(2, 1));
	t.insert(std::pair<int, int>(3, 1));
	t.erase(t.begin(), t.end());

Signed-off-by: Ben Kelly <ben@benjii.net>