libbfd: Update the bfd-aux.h.

Signed-off-by: Alex Wang <alexw@nicira.com>
monitor: Add monitor.{c,h}

This module abstracts the tunnel monitoring logic.  It is designed
that the module can be used to monitor multiple protocols (e.g. bfd,
cfm) at the same time.

Note:
- The code and support libraries are directly copied from the Open
  Vswitch.  Next step is to make those code generic.

Signed-off-by: Alex Wang <alexw@nicira.com>
monitor: Apply refinement from the Open Vswitch porting.

Signed-off-by: Alex Wang <alexw@nicira.com>
monitor: Add monitor-aux.h.

Signed-off-by: Alex Wang <alexw@nicira.com>
Merge branch 'monitor' of https://github.com/yew011/libbfd into monitor