* Insert LDAP, FTP, SSH, IMAP, POP, RADIUS checkers.
* documentation:
	- hackers guide
* code cleanup:
	- check_ssl.c audit the password_cb() call back func
	  for buffer overflow.
	- check smtp.c to release allocated buffer when terminate
	  thread is registered. Occur when sigint is receive when
	  smtp alertes have not been able to finish the whole sending
	  sequence.
* more choice with parameters, less hardcoded values
* functionality:
	- hooks in VRRP framework for external checktools.
	  As state transition decision
	- a VTYSH to administrate keepalived on the fly
