Fold pretag parse state into tag parse state.  It makes no sense to try to put xml preamble and entity processing in another module.  The code is not complete yet but the basic idea is fleshed out now.

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/branches/CONNECTORS-633@1443307 13f79535-47bb-0310-9956-ffa450edef68