Give wider types to sscanf to fix two warnings (u_short cannot be > 0xffff)

Give wider types to sscanf to fix two warnings (u_short cannot be > 0xffff)
and to make sure that we catch oversized arguments rather than silently
truncate them.  I dont know if sscanf will reject an integer if it will
not fit in the short return variable or not, but this way it should be
detected.