Merge into master from pull request #33:
convert flow modify and aggregate stats to long running tasks (https://github.com/floodlight/indigo/pull/33)
Add indigo_cxn_connection_config_get.
Add error checking for cxn_id.
Merge into master from pull request #35:
Add indigo_cxn_connection_config_get. (https://github.com/floodlight/indigo/pull/35)
OFCONNECTIONMANAGER_CONFIG_ECHO_OPTIMIZATION

Allow compile-time specification of echo generation behavior.

- OFCONNECTIONMANAGER_CONFIG_ECHO_OPTIMIZATION == 1
  Echo requests are only sent when the controller connection is idle.
  (This was the existing behavior).

- OFCONNECTIONMANAGER_CONFIG_ECHO_OPTIMIZATION == 0
  Echo requests are generated every 10 seconds, regardless of other activity.

  This avoids long periods of silence between the switch and controller when
  when the switch is busy processing messages which generate no replies.
Clear revents when registering a new socket.
Otherwise, stale revents would trigger an immediate call to the
newly registered callback.
Merge into master from pull request #38:
Clear revents when registering a new socket. (https://github.com/floodlight/indigo/pull/38)
It doesn't appear this is required to solve the intended problem given the current management of the oustanding echo request count.
Merge into master from pull request #37:
OFCONNECTIONMANAGER_CONFIG_ECHO_OPTIMIZATION (https://github.com/floodlight/indigo/pull/37)
Merge into master from pull request #34:
Dynamic flowtable entry allocation (https://github.com/floodlight/indigo/pull/34)
OFStateManager: move ptr_cxn_wrapper_t to the internal header

ofstatemanager.c needs this.
OFStateManager: fix bug when marking for deletion

ft_entry_mark_deleted always set the state to DELETE_MARKED whether or not the
flow was stable, so we'd always make the call into forwarding immediately (even
if the previous state was MODIFYING, meaning we'd have two requests in flight
for the same flow!).

The fix is to only send the call to forwarding if the flow was stable before
marking it for deletion.
OFStateManager: fix barrier tracking for flow deletes

Previously, the delete message handlers would free the LOCI message immediately
without waiting for Forwarding to signal that the deletion was complete. This
meant pending deletions would not block a barrier.

This change passes the usual ptr_cxn_wrapper_t as the cookie to
indigo_fwd_flow_delete instead of just the entry pointer. The ptr_cxn retains
the LOCI request for barrier tracking.

The queued request code is changed significantly. Previously (contrary to the
comments) a deletion was not tracked on the queued_reqs list. Now the ptr_cxn
is enqueued and any existing queued modifies are deleted.