webfs: add error code 405
 [rsc] --rw-rw-r-- M 136171 glenda sys 9487 Mar  6 11:25 sys/src/cmd/webfs/http.c
	/n/sourcesdump/2006/0306/plan9/sys/src/cmd/webfs/http.c:387,392 - 
	/n/sourcesdump/2006/0307/plan9/sys/src/cmd/webfs/http.c:387,396
	  		werrstr("Not found on server (404)");
	  		goto Error;
	  
	+ 	case 405:	/* Method Not Allowed  */
	+ 		werrstr("Method not allowed (405)");
	+ 		goto Error;
	+ 
	  	case 407:	/* Proxy auth */
	  		werrstr("Proxy authentication required (407)");
	  		goto Error;