include/openflow: Add OpenFlow 1.4 header file

It contains only Set-Async-Config and Role status message definitions.

Signed-off-by: Alexandru Copot <alex.mihai.c@gmail.com>
Cc: Daniel Baluta <dbaluta@ixiacom.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
ofproto: Add support for sending OFPTYPE_ROLE_STATUS messages.

When a controller changes its role to MASTER, the others are marked
as SLAVE. This patch makes it possible to notify the controllers
of this change.

Signed-off-by: Alexandru Copot <alex.mihai.c@gmail.com>
Cc: Daniel Baluta <dbaluta@ixiacom.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>