Bug#653750: positioning important -->> positioning is important?

[Regid Ichira]

  Is there a missing `is'?

--- a/spec.txt  2012-02-29 13:52:04.040177501 +0200
+++ b/spec.txt  2012-02-29 13:48:40.000000000 +0200
@@ -24247,7 +24247,7 @@ others specify text for messages that ar
 warning is generated. The control modifier affects the way an incoming message
 is handled.

-The positioning of the modifiers in an ACL statement important, because the
+The positioning of the modifiers in an ACL statement is important, because the
 processing of a verb ceases as soon as its outcome is known. Only those
 modifiers that have already been encountered will take effect. For example,
 consider this use of the message modifier: