netinet/in.h: add INADDR_ALLSNOOPERS_GROUP from linux v5.1

RFC 4286: "The IPv4 multicast address for All-Snoopers is 224.0.0.106."
from

  linux commit 4effd28c1245303dce7fd290c501ac2c11052114
  bridge: join all-snoopers multicast address
1 file changed