change the signature of ap_custom_response() to use a

"const char *" instead of a "char *".


PR: 8791
Submitted by: Kurt Brown kurtb149@yahoo.com
Reviewed by:	Ian Holsman


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@92024 13f79535-47bb-0310-9956-ffa450edef68