now that jlemon has added a hash table to lookup locally configured ip

addresses (and the macros that ipfw(4) use to lookup data for the 'me'
keyword have been converted) remove a comment about using 'me' being a
"computationally expensive" operation.

while I'm here, change two instances of "IP number" to "IP address"

sbin/ipfw/ipfw.8

@@ -500,12 +500,11 @@ keywords mean any protocol will match.
 .Pp
 Specifying
 .Cm any
-makes the rule match any IP number.
+makes the rule match any IP address.
 .Pp
 Specifying
 .Cm me
-makes the rule match any IP number configured on an interface in the system.
-This is a computationally semi-expensive check which should be used with care.
+makes the rule match any IP address configured on an interface in the system.
 .Pp
 The
 .Aq Ar address Ns / Ns Ar mask