LCL: Start replacing TEditButton with TButtonEdit component.
The old TEditButton implementation is (for the time being) compilable with -dUSEOLDEDITBUTTON


git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@44623 4005530d-fff6-0310-9dd1-cebe43e6787f