Make RfcGetVersion accessible

[datenimperator]

We use Ruby and SAP in production, and it'd be awesome to be able to tell from Ruby which release of librfc is currently linked to it. There's a function const SAP_UC* SAP_API RfcGetVersion(unsigned* majorVersion, unsigned* minorVersion, unsigned* patchLevel)in the SDK for this but AFAICT it's not available from Ruby yet.

[piersharding]

Hi -

I've added SAPNW::RFC.LibVersion() to the latest version.

Cheers,
Piers Harding.