Add support for out-of-band messages during eval

[edi-bice]

I need to be able to send progress messages from R code via node-rio to my Node server. RServe 1.7 added OOB messages (see below) and I was wondering if node-rio can be changed to support it.

http://rforge.net/Rserve/dev.html

"""Starting with 1.7 Rserve can support (when enabled) out-of-band (OOB) commands, which is nested communication during an eval. OOB messages are initited by evaluated R code (typically via self.oobSend or self.oobMessage). Each OOB message has the CMD_OOB bitmask set to distinguish it from a regular command/response. Two classes of messages exist: OOB_SEND is uni-directional (from server to client), OOB_MSG is bi-directional (request from server to client, expecting a response from client to server). If a client doesn't support OOB, it MUST either abort the connection or send ERR_unsupportedCmd when encountering OOB_MSG to avoid a deadlock (eval will not finish until OOB_MSG receives a response)."""

[albertosantini]

I will give a look at it in the next days.

[albertosantini]

In Windows environment (my main dev env) it seems the object-capability support is missing, Rserve:::ocap object is not available.

See note about Rserve 1.7.0 about many of the new features rely on things lacking in Windows.
http://rforge.net/Rserve/

Anyway I would be glad a contribution for unix users.

[albertosantini]

I close this issue because it is a "won't fix".

Of course I will accept any PR about the theme.