EditButton: refactor.
(Rename TBeEdit to TEbEdit, the old name was short for TButtonEditEdit, which was thought up
at the time the TEditButton was rewritten as TButtonEdit.)


git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@44702 4005530d-fff6-0310-9dd1-cebe43e6787f