Ensure the IDL p4 filter can cope with recursive types

Signed-off-by: Jon Ludlam <jonathan.ludlam@eu.citrix.com>
Merge pull request #15 from jonludlam/recursive-idl-types

Ensure the IDL p4 filter can cope with recursive types
Fix an minor issue with Xmlrpc and make Jsonrpc and Xmlrpc more alike

Jsonrpc already had to_fct whereas Xmlrpc had to_a, both quite similar.
I've opted to implement to_a in Jsonrpc, mostly because in xen-api-libs
we didn't have the to_fct exposed in our copy of Jsonrpc.

Signed-off-by: Jon Ludlam <jonathan.ludlam@eu.citrix.com>
Merge pull request #16 from jonludlam/more-fixes

Fix an minor issue with Xmlrpc and make Jsonrpc and Xmlrpc more alike