64-bit fixes.
 [jmk] --rw-rw-r-- M 107020 glenda sys 1160 Nov 19 21:15 sys/src/libip/ptclbsum.c
	/n/sourcesdump/2005/1119/plan9/sys/src/libip/ptclbsum.c:17,23 - 
	/n/sourcesdump/2005/1120/plan9/sys/src/libip/ptclbsum.c:17,23
	  	mdsum = 0;
	  
	  	x = 0;
	- 	if((ulong)addr & 1) {
	+ 	if((uintptr)addr & 1) {
	  		if(len) {
	  			hisum += addr[0];
	  			len--;