Ronald Landheer-Cieslak points out that the various back ends which

Ronald Landheer-Cieslak points out that the various back ends which
treat all socket closures as clean exits (because the protocol doesn't
provide for transferring a process exit code) could usefully at least
treat _socket errors_ as unclean exits. Patch the Telnet, Rlogin and
Raw backends to retain that information and return INT_MAX to the
frontend.

I wasn't sure whether it was better to solve this by modifying each
affected frontend, or each affected backend. I chose the latter, but
neither is really ideal; this is the sort of thing that makes me wish
we had a piece of fixed middleware in between, independent of both
platform and protocol.

[originally from svn r9730]