LCL, grids, fix Title.Caption is not changed if new value is one char and current caption value starts with the same char, seems FCaption^ is not anymore treated as a string but as a char)

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@45343 4005530d-fff6-0310-9dd1-cebe43e6787f