Ahaggar: make the match callback functions a typedef

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: add the logic to store dynamic messages returned by matches

* Add the tmp_message buffer support to hold messages generated
  dynamicaly
* Make the patter_match->msg_extra point to the static tmp_message
  buffer. The pattern_match->msg_extra should be filled by callback
  matchers.
  We do this to reduce memory consumption, so all the patterns will have
  the same buffer. We make sur to report and clean the buffer before the
  next call.

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>