can't pass const char * to ap_strchr()

(note that when AP_DEBUG is on, strchr() maps to ap_strchr() so we
find abuses of the broken strchr() interface)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@90211 13f79535-47bb-0310-9956-ffa450edef68