ChannelMergerNode mixing semantics seem weird in dynamic situations

ChannelMergerNode seems a bit fragile if the number of channels on an input
is changing dynamically. The way it's defined, if the number of channels on
input 0 changes dynamically, then the channels of inputs > 0 move up or
down in the channel layout. The same thing would happen if a node is
connected or disconnected to input 0 while other nodes are connected to
inputs > 0. In fact, the spec doesn't say what happens if input 0 has
nothing connected but inputs > 0 do.

It seems ChannelMergerNode would also interact poorly with the auto-removal
of nodes from the graph (which is still itself a big problem ... I posted
about that a while ago).

I think it would be much simpler and more reliable, and easier to
implement, if the number of channels taken from each input by
ChannelMergerNode was constant for the lifetime of the node. For example,
we could pass this as an additional optional parameter to
createChannelMerger, defaulting to 1.

Rob
-- 
Jesus called them together and said, “You know that the rulers of the
Gentiles lord it over them, and their high officials exercise authority
over them. Not so with you. Instead, whoever wants to become great among
you must be your servant, and whoever wants to be first must be your
slave — just
as the Son of Man did not come to be served, but to serve, and to give his
life as a ransom for many.” [Matthew 20:25-28]