DPS Code does not correctly add Start/End dates to memberships

I came across issue with the DPS payment express payment processor when using a contribution page that creates memberships - When the IPN callback is made, the payment is changed to completed but the attached membership is not updated with starting/ending dates.

Reproduce: 1. Create a contribution page using DPS which creates memberships
2. Put a payment through with that page.
3. The membership still has pending status, even after the 'Approved' IPN call.

I tracked the problem to this code in PaymentExpressIPN.php:

// Private Data consists of : a=contactID, b=contributionID,c=contributionTypeID,d=invoiceID,e=membershipID,f=participantID,g=eventID
$privateData['contactID'] = $privateData['a'];
$privateData['contributionID'] = $privateData['b'];
$privateData['contributionTypeID'] = $privateData['c'];
$privateData['invoiceID'] = $privateData['d'];

if ( $component == "event" )

{ $privateData['participantID'] = $privateData['f']; $privateData['eventID'] = $privateData['g']; }

else if ( $component == "contribute" ) {

if ( count($privateData) == 5)

{ $privateData["membershipID"] = $privateData['e']; }

}

Which checks that the count($privateData) = 5 to determine if this is a membership-attached contribution, but since the earlier code just added 4 items to the array the correct magic number is 9.

Attached is a patch which fixes this by recording the count before beginning to add details to $privateData, and comparing against that.