Fixed bug when appending one SString to another with +=.
Fixed bug when appending one SString to another with +=.

windoze/scintilla,keperlia/foo-wsh-panel-mod.scintilla,windoze/scintilla,keperlia/foo-wsh-panel-mod.scintilla,keperlia/foo-wsh-panel-mod.scintilla,keperlia/foo-wsh-panel-mod.scintilla,windoze/scintilla,windoze/scintilla,windoze/scintilla,keperlia/foo-wsh-panel-mod.scintilla,windoze/scintilla,keperlia/foo-wsh-panel-mod.scintilla,windoze/scintilla,windoze/scintilla