This commit adds (some) support for a couple new OpenFlow 0.9 features:
- The OFPFF_CHECK_OVERLAP flag in Flow Mod messages allows the
controller to prevent flows that would conflict at the same
priority.
- An emergency flow cache that contains a small flow table that is
used if the switch loses connectivity with the controller. I
believe the design has fundamental flaws and looks likely to be
retired. If a controller attempts to add a flow to the emergency
flow cache, OVS always responds that the tables are full.
The OpenFlow 0.9 error codes are also sync'd in the commit.
NOTE: OVS at this point is not wire-compatible with OpenFlow 0.9 until the
final commit in this OpenFlow 0.9 set.
Starting in OpenFlow 0.9, it is possible to match on the VLAN PCP
(priority) field and rewrite the IP ToS/DSCP bits. This check-in
provides that support and bumps the wire protocol number to 0x98.
NOTE: The wire changes come together over the set of OpenFlow 0.9 commits,
so OVS will not be OpenFlow-compatible with any official release between
this commit and the one that completes the set.
This prepares for adding a new function that deals with a "struct hmap"
moving, as opposed to a "struct hmap_node".
Since there was only a single call to this in the whole tree, and its
caller didn't have any callers of its own at all, also move this function
from hmap.h to hmap.c.
