Merge branch 'tipc-improvements-to-group-messaging'

Jon Maloy says:

====================
tipc: improvements to group messaging

We make a number of simplifications and improvements to the group
messaging service. They aim at readability/maintainability of the code
as well as scalability.

The series is based on commit efb7a104081e ("tipc: fix problems with
multipoint-to-point flow control) which has been applied to 'net' but
not yet to 'net-next'.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>