frontend: add name to OFInput

Just useful for debugging.
loxigen: allow structs to refer to enums in other input files

Do a first pass over the input files to extract the enums.

Also hoists the OFProtocol construction from the loop over inputs. It only
needs to be done once.
openflow_input: add BSN LACP stats request

This extension allows the controller to query LACP configuration and state from
the switch.
pyloxi: support of_bsn_lacp_stats_request/reply
java_gen: support of_bsn_lacp_stats_request/reply
loci: support of_bsn_lacp_stats_request/reply