sfbits: reset bufpos/bufend on init

sfbits.c

@@ -100,5 +100,7 @@ void init_bits_sf(struct bitreader *b, SNDFILE *f, int xbit)
 	b->fill_bits = fill_bits;
 
 	file = f;
+	bufpos = 0;
+	bufend = 0;
 	xorbit = xbit + 8;
 }