Usage update.
 [rsc] --rw-rw-r-- M 318707 jmk sys 13922 Dec 15 10:16 sys/src/cmd/aux/msexceltables.c
	/n/sourcesdump/2005/1215/plan9/sys/src/cmd/aux/msexceltables.c:703,709 - 
	/n/sourcesdump/2005/1216/plan9/sys/src/cmd/aux/msexceltables.c:703,709
	  void
	  usage(void)
	  {
	- 	fprint(2, "usage: %s [-aDnt] [-d delim] file.xls\n", argv0);
	+ 	fprint(2, "usage: %s [-aDnt] [-d delim] /mnt/doc/Workbook\n", argv0);
	  	exits("usage");
	  }