Add the functorised functions to the RRDD interface.
Add the functorised functions to the RRDD interface.

Signed-off-by: John Else <37b74501daa612e48fea94f9846ed4ddeb6a8f07@citrix.com>

Chunjie/xcp-idl,euanh/xcp-idl,xapi-project/message-switch,djs55/xcp-idl,xapi-project/message-switch,johnelse/xcp-idl,xapi-project/message-switch