win32: remove unneeded SetText implementation for WS classes - it is enough to have only one implementation in TWin32WSWinControl class. Replace SetWindowText with WM_SETTEXT since SetWindowText do nothing more than checking handle owner and calling WM_SETTEXT.

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41697 4005530d-fff6-0310-9dd1-cebe43e6787f