Revert the UnSetIfZero directive that was added when mod_setenvif

	was made a standard module.  It isn't broad enough in scope; it
	only affects those envariables set with the SetEnvIf* directives.

Reviewed by:	Dean Gaudet


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@79069 13f79535-47bb-0310-9956-ffa450edef68