yesterday: make yesterday -d match documentation
 [rsc] --rwxrwxr-x M 1695424 glenda sys 2439 Feb 24 16:22 rc/bin/yesterday
	/n/sourcesdump/2006/0224/plan9/rc/bin/yesterday:27,34 - 
	/n/sourcesdump/2006/0225/plan9/rc/bin/yesterday:27,34
	  }
	  
	  fn Xdiff {
	- 	echo diff -n $1 $2
	- 	diff -n $1 $2
	+ 	echo diff $1 $2
	+ 	diff $1 $2
	  }
	  fn Xdiffn {
	  	echo diff -n $1 $2