Pull up following revision(s) (requested by tron in ticket #940):
	lib/libc/stdlib/_env.c: revision 1.8
Don't scrub the environment unless we are going to change it. This should
prevent crashes in applications which carefully and manually construct
a temporary environment and later restore the original environment
like Emacs 24.
Problem reported by Thomas Klausner on "pkgsrc-users" mailing list.
ticket 940