Fix a problem with the display of empty variables ("SetEnv foo") in

mod_include.  Now it works like 1.3 (see PR for details).  Setting
of envvars for scripts was/is consistent with 1.3 for empty variables.

PR:           24734
Submitted by: Markus Julen <mj zermatt.net>
Reviewed by:  Jeff Trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@101830 13f79535-47bb-0310-9956-ffa450edef68