FCPPluginClient: Add draft of function for splitting synchronous message
dispatching code out of send()

- A shorter name is not necessary here IMHO:
* This function will only be used in one place for now. So it is more
important that its absolutely clear what it does.
* The "maybe" is needed to differentiat to the
dispatchMessageByNetworked() which will always succeed. This function
here might return false to indicate that the message has to be
dispatched by other means
* The "DispatchMessageLocally" is needed to be symmetric with
dispatchMessageByNetwork
* The "ToSynchronousSendThread" is needed to differentiate to the other
local message dispatching function which will follow (for dispatching to
a FredPluginFCPMessageHandler)
- The @see is a copypaste of the one at sendSynchronous()