oc: Return FAI available properties on instance method as well

The operation RopFastTransferSourceCopyTo calls the available
properties for a message using the instance method. It seems the
preferred method by Outlook to synchronise a FAI message. OpenChange
calls the message to get the available properties, so the instance
method is called. As it is specialised to return the custom hack
FAI properties, we have to call that class method instead of using
generic one available at NSObject (MAPIStoreProperties) class.

This avoids crashing the Outlook client after we synchronise the
calendar folder after changing the timeframe view (eg from day view
to month view).

OpenChange/MAPIStoreDBMessage.m

@@ -76,6 +76,13 @@
   return MAPISTORE_SUCCESS;
 }
 
+- (enum mapistore_error) getAvailableProperties: (struct SPropTagArray **) propertiesP
+                                       inMemCtx: (TALLOC_CTX *) memCtx
+{
+  return [[self class] getAvailableProperties: propertiesP
+                                     inMemCtx: memCtx];
+}
+
 - (id) initWithSOGoObject: (id) newSOGoObject
               inContainer: (MAPIStoreObject *) newContainer
 {