This partially reverts commit 561078480ffb5adb68577276c6b23e4ee7b39272.

If we avoid all debug mode checks when erasing elements then we fail to
invalidate safe iterators to the removed elements. This reverts the
recent changes in r12-4083 and r12-4233, restoring the debug checking.

libstdc++-v3/ChangeLog:

	* include/experimental/deque (erase, erase_if): Revert changes
	to avoid debug mode overhead.
	* include/experimental/map (erase, erase_if): Likewise.
	* include/experimental/set (erase, erase_if): Likewise.
	* include/experimental/unordered_map (erase, erase_if):
	Likewise.
	* include/experimental/unordered_set (erase, erase_if):
	Likewise.
	* include/experimental/vector (erase, erase_if): Likewise.
	* include/std/deque (erase, erase_if): Likewise.
	* include/std/map (erase, erase_if): Likewise.
	* include/std/set (erase, erase_if): Likewise.
	* include/std/unordered_map (erase, erase_if): Likewise.
	* include/std/unordered_set (erase, erase_if): Likewise.
	* include/std/vector (erase, erase_if): Likewise.

Tested powerpc64le-linux. Committed to trunk.