Support for removing legacy :doc strings from ACL2 sources.

git-svn-id: http://acl2-books.googlecode.com/svn/trunk@2398 303c5b2c-9740-0410-b014-fd8f9db7be32
fixes (i think?) to remove unnecessary parent hacking from xdoc::save

git-svn-id: http://acl2-books.googlecode.com/svn/trunk@2399 303c5b2c-9740-0410-b014-fd8f9db7be32
Did proper removal this time of two empty top-level topics from the ACL2 manual.  (Thanks to Jared for help with this!).

git-svn-id: http://acl2-books.googlecode.com/svn/trunk@2400 303c5b2c-9740-0410-b014-fd8f9db7be32