64-bit fix.
 [rsc] --rw-rw-r-- M 733409 glenda sys 3126 Oct  2 08:11 sys/src/cmd/9660srv/iobuf.c
	/n/sourcesdump/2005/1002/plan9/sys/src/cmd/9660srv/iobuf.c:42,48 - 
	/n/sourcesdump/2005/1003/plan9/sys/src/cmd/9660srv/iobuf.c:42,48
	  
	  	n = NCLUST*sizeof(Ioclust)+NCLUST*BUFPERCLUST*(sizeof(Iobuf)+Sectorsize);
	  	mem = sbrk(n);
	- 	if((long)mem == -1)
	+ 	if(mem == (void*)-1)
	  		panic(0, "iobuf_init");
	  	memset(mem, 0, n);