Resource allocation in protocol handlers

[coot]

@dcoutt noted:

It's probably a general thing we should clarify in our docs for typed protocols
and the network framework etc:Do not allocate resources within a protocol
handler. Have all resources allocated (with appropriate bracketing) and passed
into the protocol handler.Protocol handlers get killed unceremnoiusly, and the
(continuation) style in which they are written does not support resource
cleanup.

[coot]

This should be documented in typed-protcols haddocks.