lcl: don't insert Enter key to TMemo if WantReturns is set to False

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41673 4005530d-fff6-0310-9dd1-cebe43e6787f
gtk2: don't eat KeyUp if KeyPress event has handled a key - a part of fix for TMemo.WantReturns

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41674 4005530d-fff6-0310-9dd1-cebe43e6787f
qt: don't skip Enter,Return,Backspace for UTF8KeyPress as other widgetsets does not do so

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41675 4005530d-fff6-0310-9dd1-cebe43e6787f