httpd(8): document @ in httpd.rewrite
 [rsc] --rw-rw-r-- M 842976 glenda sys 6866 Mar 19 14:15 sys/man/8/httpd
	/n/sourcesdump/2006/0319/plan9/sys/man/8/httpd:136,141 - 
	/n/sourcesdump/2006/0320/plan9/sys/man/8/httpd:136,149
	  but not both:
	  .B http://system/who/rob
	  will never match a request.
	+ .I Httpd
	+ handles replacements prefixed with 
	+ .B @ 
	+ internally,
	+ treating the request as if it were for the replacement
	+ (without the
	+ .BR @ )
	+ but not informing the client of the rewritten name.
	  .PP
	  Before opening any file,
	  .I httpd