Remove lmenu dependency in beanshell.el.

lmenu has been obsolete in GNU Emacs since 23.3. Since we're still
pretending to support XEmacs we simply don't add the menu item when
running in XEmacs. Fixes Bug #34.

git-svn-id: svn+ssh://svn.code.sf.net/p/jdee/code/trunk@297 381a1f10-3442-0410-997e-ef331cd04102