eat unrecognized characters.  i was having trouble with the alt key
generating a pc linedrawing character.  worse,
	create /<altkey> user user 544
will create a difficult-to-delete file.

Notes:
There is a real problem with accidentally typing invisible characters
on the file server console.

I'm rejecting this patch but will soon push out a change to devcons.c
to make invisible characters echo.

Reference: /n/sources/patch/sorry/fs-eatctl
Date: Thu Aug 17 20:34:08 CES 2006
Signed-off-by: quanstro@quanstro.net
Reviewed-by: geoff

--- /sys/src/fs/pc/kbd.c	Thu Aug 17 20:29:14 2006
+++ /sys/src/fs/pc/kbd.c	Thu Aug 17 20:29:08 2006
@@ -277,7 +277,7 @@
 			return -1;
 		}
 	}
-	return c;
+	return -1;
 }
 
 static void