Add quick leave feature for leave report

If you want improxy leave group immediately when it receives leave
report, Please add "quickleave enable" into its config file, default value
is disable.
Filter IPv4 Local Scope(239.255.0.0/16) on upstream interface

239.255.0.0/16 is defined to be the IPv4 Local Scope in RFC 2365.
Improxy must not join this kind of group address on upstream interface