now if there is no selection and the last character is an operator: + - / * % ^ (
then the text is append at the end (instead of looking for beginning of the expression)
this seems to be more comfortable
git-svn-id: svn://ttmath.org/publicrep/ttcalc/trunk@353 e52654a7-88a9-db11-a3e9-0013d4bc506e