added parsing of  and  of the endsequent (workaround to prevent special handling of top and bottom symbols: replace by trivial valid/unsat formula -- this will confis Robinson2LK) and added variable renaming of free variables of the endsequent

git-svn-id: http://gapt.googlecode.com/svn/trunk/source@1393 85d21ef8-add0-11de-ae77-5bfb9c5a3f34