Replace ap_expr with a parser derived from mod_ssl's parser. Make mod_ssl use

the new parser. Rework ap_expr's public interface and provide hooks for modules
to add variables and functions.

The Netware and Windows build files still need to be adjusted


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1032073 13f79535-47bb-0310-9956-ffa450edef68