Fix usage.
 [rsc] --rw-rw-r-- M 771144 glenda sys 2257 Feb 11 15:33 sys/man/1/grep
	/n/sourcesdump/2006/0211/plan9/sys/man/1/grep:8,18 - 
	/n/sourcesdump/2006/0212/plan9/sys/man/1/grep:8,18
	  ]
	  [
	  .B -e
	+ ]
	  .I pattern
	- [
	+ |
	  .B -f
	  .I patternfile
	- ]
	  [
	  .I file ...
	  ]
 [rsc] --rw-rw-r-- M 771144 glenda sys 2257 Feb 11 15:33 sys/man/1/grep