Make clear that negative matches must not appear anywhere in the string

src/dcs_demo.db

@@ -14,11 +14,12 @@
 # substr	type
 # substr*substr*substr	type
 # !substr*substr	type
+# substr*!substr	type
 # #
 # substr is matched anywhere in the User-Agent header
 # substr can contain spaces, but not tabs
 # for a successful match on the entry, all substrs must match
-# negative matches are marked with a !
+# and no negative matches (marked with !) must appear anywhere
 #
 # first match wins
 #