add the support to Long string #508

[dreamershl]

No description provided.

[dcodeIO]

This is working now. Note, though, that always converting hence and forth between longs and strings is slow. Ideally, when encoding a message multiple times, the value should be present as a long instead of a string to prevent multiple conversions.

[dreamershl]

Thank u very much. the converting is only done when send/receive the message from the server in my system. So it should be fine.