INSTALL: mention sbcelt.h.
INSTALL: mention sbcelt.h.

mumble-voip/sbcelt,SuperTux88/sbcelt,mkrautz/sbcelt,mumble-voip/sbcelt,mumble-voip/sbcelt,mumble-voip/sbcelt,SuperTux88/sbcelt,mkrautz/sbcelt,SuperTux88/sbcelt,mkrautz/sbcelt,mkrautz/sbcelt,SuperTux88/sbcelt