the html files used for chm compiling differ in detail from our normal

manual pages. The target format is reflected by the $is-chm variable
which is used to <if> in and out the interesting parts.

Further add some more utility snippets.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@99409 13f79535-47bb-0310-9956-ffa450edef68