major overhaul of mod_include's filter parser. Note that the new code

contains a thin wrapper to ensure binary compatibility. (needed for
2.0 backport).

This is a two-tiered commit for better diffs. This one inserts the new
code (old code #if'd out).


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@101036 13f79535-47bb-0310-9956-ffa450edef68