Fix tar's handling of links.
 [rsc] --rw-rw-r-- M 23749 glenda sys 22453 Jan 31 07:50 sys/src/cmd/tar.c
	/n/sourcesdump/2006/0131/plan9/sys/src/cmd/tar.c:56,62 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/cmd/tar.c:56,62
	  	LF_PLAIN2 =	'0',
	  	LF_LINK =	'1',
	  	LF_SYMLINK1 =	'2',
	- 	LF_SYMLINK2 =	's',
	+ 	LF_SYMLINK2 =	's',		/* 4BSD used this */
	  	LF_CHR =	'3',
	  	LF_BLK =	'4',
	  	LF_DIR =	'5',
	/n/sourcesdump/2006/0131/plan9/sys/src/cmd/tar.c:459,470 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/cmd/tar.c:459,471
	  	return name(hp)[0] == '\0';
	  }
	  
	+ /* return the size from the header block, or zero for links, dirs, etc. */
	  Off
	  hdrsize(Hdr *hp)
	  {
	  	Off bytes = strtoull(hp->size, nil, 8);
	  
	- 	if(isdir(hp))
	+ 	if(isdir(hp) || islink(hp->linkflag))
	  		bytes = 0;
	  	return bytes;
	  }
	/n/sourcesdump/2006/0131/plan9/sys/src/cmd/tar.c:934,939 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/cmd/tar.c:935,942
	  	} else
	  		print("%s\n", fname);
	  
	+ 	if (blksleft == 0)
	+ 		bytes = 0;
	  	for (; blksleft > 0; blksleft -= blksread) {
	  		hbp = getblkrd(ar, (fd >= 0? Alldata: Justnxthdr));
	  		if (hbp == nil)
	/n/sourcesdump/2006/0131/plan9/sys/src/cmd/tar.c:940,945 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/cmd/tar.c:943,951
	  			sysfatal("unexpected EOF on archive extracting %s",
	  				fname);
	  		blksread = gothowmany(blksleft);
	+ 		if (blksread <= 0)
	+ 			fprint(2, "%s: got %ld blocks reading %s!\n",
	+ 				argv0, blksread, fname);
	  		wrbytes = Tblock*blksread;
	  		if(wrbytes > bytes)
	  			wrbytes = bytes;
	/n/sourcesdump/2006/0131/plan9/sys/src/cmd/tar.c:948,953 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/cmd/tar.c:954,963
	  		putreadblks(ar, blksread);
	  		bytes -= wrbytes;
	  	}
	+ 	if (bytes > 0)
	+ 		fprint(2,
	+ 		    "%s: %lld bytes uncopied at eof; %s not fully extracted\n",
	+ 			argv0, bytes, fname);
	  	if (fd >= 0) {
	  		/*
	  		 * directories should be wstated after we're done