First step towards extracting the SSI handling from mod_include so that

it is extensible by modules
Submitted by:	Paul J. Reder <rederpj@raleigh.ibm.com>
Reviewed by:	Ryan Bloom


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@87113 13f79535-47bb-0310-9956-ffa450edef68