Fix assertions for move assignment of trivial types

Fix assertions for move assignment of trivial types

Backport from mainline
2016-01-26  Jonathan Wakely  <jwakely@redhat.com>

	PR libstdc++/69478
	* include/bits/stl_algobase.h (__copy_move<_IsMove, true,
	random_access_iterator_tag>): Check is_move_assignable when moving.
	(__copy_move_backwards<_IsMove, true, random_access_iterator_tag>):
	Likewise.
	* testsuite/25_algorithms/copy/move_iterators/69478.cc: New.
	* testsuite/25_algorithms/copy_backward/move_iterators/69478.cc: New.
	* testsuite/25_algorithms/move/69478.cc: New.
	* testsuite/25_algorithms/move_backward/69478.cc: New.

From-SVN: r235285