Add SNMP subsystem option to man page

The keepalived(8) man page did not mention the -x option to enable the
SNMP subsystem. This patch adds the -x (and --smmp) options to the
keepalived(8) man page, as described in the keepalived help message.
Merge pull request #91 from rohara/keepalived-man-snmp

Add SNMP subsystem option to man page
vrrp: fix gratuitous ARP refresh timer handling

Previous code was using an 'int' to store parsed timer value. This value
was then expanded to TIMER_HZ which can lead to a wrapping issue if
requested timer is longer than local machine 'int' representation.

This patch reworked the code to use timeval_t instead and perfrom
regular timeval operations.
vrrp: Fix a memory leak while dropping incoming IPSEC-AH authenticated advert.

Jay True fixed a memory leak in IPSEC-AH sanity check. Digest was allocated in
previous code without freing it on HMAC-MD5 missmatch. good catch Jay !
vrrp: Extend IPSEC-AH auth to support unicast

If you plane to use IPSEC-AH auth in unicast mode (which THE best idea), then
IP header TTL MUST be zeroed since it is mutable field on transit.
vrrp: Update VRRP VMAC doc

Add vmac_xmit_base in configuration example and force rp_filter=0 on
macvlan interface.
vrrp: make gratuitous ARP repeat count configurable

Patrick Schaaf and I introduced 2 new keywords :

* garp_master_repeat : Gratuitous ARP count sent on the wire
                       after MASTER state transition.

* garp_master_refresh_repeat : Gratuitous ARP count sent on the
                               wire when garp_refresh_timer fired.
vrrp: fix preempt and state BACKUP when prio 255

This makes it so that keepalived will respect various settings that
should prevent it from assuming the MASTER role for a vrrp_instance
unconditionally and immediately, even if the priority of the
vrrp_instance in question is set to 255 (VRRP_PRIO_OWNER). These
settings include:

  state BACKUP
  preempt_delay <N>
  nopreempt
Merge pull request #102 from toreanderson/fix-prio-255

vrrp: fix preempt and state BACKUP when prio 255
ipvs: failed RS was flapping on config reload

The RS disabled by health-checker was turned on w/o health-checking
by SIGHUP handler in the init_service_rs() subroutine.
This did not happen with alpha mode set.

The issue was reported by Luis Fernando Cornachioni Estrozi
in the keepalived-devel@ list.