PR libstdc++/61086
	* include/bits/stl_iterator.h (__normal_iterator::_M_const_cast):
	Remove.
	* include/bits/stl_vector.h (vector::insert, vector::erase): Use
	arithmetic to obtain a mutable iterator from const_iterator.
	* include/bits/vector.tcc (vector::insert): Likewise.
	* include/debug/vector (vector::erase): Likewise.
	* testsuite/23_containers/vector/requirements/dr438/assign_neg.cc:
	Adjust dg-error line number.
	* testsuite/23_containers/vector/requirements/dr438/
	constructor_1_neg.cc: Likewise.
	* testsuite/23_containers/vector/requirements/dr438/
	constructor_2_neg.cc: Likewise.
	* testsuite/23_containers/vector/requirements/dr438/insert_neg.cc:
	Likewise.

From-SVN: r210162