We already had in place the blockSizeAcceptLimit as the limit
on messages, which is now the only limit.
In practice this means when the operator sets the maximum mining
size that we adjust the blockSizeAcceptLimit, if they only set the
blockSizeAcceptLimit, we use that (plus a margin) to limit messages
both on the p2p layer and on the RPC (JSON) layer we change the
limit to be twice the blockSizeAcceptLimit (copied those numbers
from BCHN).
TomZ