Backport:

mod_include: Allow fine control over the removal of Last-Modified and ETag
headers within the INCLUDES filter, making it possible to cache responses if
desired. Fix the default value of the SSIAccessEnable directive.
+1: minfrin, jim, rpluem


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@917008 13f79535-47bb-0310-9956-ffa450edef68