apinger cleanup

• Add DOCS option, enabled by default
• Move docs from pkg-plist to PORTDOCS
• Use IPV6_CONFIGURE_ENABLE knob
• Make rclint happy
• Regenerate patches with make makepatch
• Add @sample to apinger.conf
• Bump PORTREVISION due to rc script changei

PR: ports/204465
Submitted by: garga
Sponsored by: Rubicon Communications (Netgate)