monitor: Refine code based on meeting discussion.

- Comment the '__ptr' in 'struct mport' as private variable.
- Combine the has_timedout_session() and get_timedout_session().
- Make the hmap, heap module generic.
- Successfully ported the code to Open Vswitch and passed all unit tests.

Signed-off-by: Alex Wang <alexw@nicira.com>
monitor: Refine the MONITOR_API.

Signed-off-by: Alex Wang <alexw@nicira.com>
libbfd+monitor: Remove the include of <config.h>.

The '#include <config.h>' is only required by the Open Vswitch.
So this commit removes it.

Signed-off-by: Alex Wang <alexw@nicira.com>