Documentation rebuild

This commit also revert my last one about H2PushResource.
After a chat on #http-dev we decided to make it public since
it holds a Compatibility section.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1769853 13f79535-47bb-0310-9956-ffa450edef68