mod_cgid: Handle environment variables containing newlines.

Communication between handler and daemon used newlines to delimit
environment variables, which threw everything off when an environment
variable contained a newline.

Communication between handler and daemon was extensively reworked.
Environment variables were handled as in the patch submitted by
Piotr Czejkowski.

PR:              14550
Submitted by:	 Piotr Czejkowski <apache@czarny.eu.org>, Jeff Trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@97530 13f79535-47bb-0310-9956-ffa450edef68