Conduit: apply the Vchan.In_memory module in addition to the network stack

This Vchan dependency being hardcoded should still work fine on Unix,
since it just defaults to the loopback Vchan model.  We will make it
disappear in a future revision that uses open types to avoid having all
the supported transport mechanisms appear as a functor argument.
Adjust http test for conduit api
travis: reduce verbosity slightly
Merge pull request #297 from avsm/master

Conduit: apply the Vchan.In_memory module in addition to the network stack
Add support for a loopback Vchan module, to satisfy the Conduit functor
Add a `VCHAN_xen` module that maps a working vchan implementation
CONSOLE is now a FLOW

This is a backwards-incompatible change which affects the following
CONSOLE functions:

  write
  write_all

Client applications need to be updated to use the new Cstruct.t based
blocking 'write' function:

  val write : flow -> buffer -> [`Ok of unit | `Eof | `Error of error ]
io

There is no non-blocking 'write' function. I believe lossy console
output functions are a mistake because they cause confusion when
debugging.

This is part of [mirage/mirage#203]

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #302 from djs55/console-flow

CONSOLE is now a FLOW
Switch to using the unified mirage-console.2.0.0 package

See mirage/mirage-dev#26 for the new package
Merge pull request #304 from avsm/unified-mirage-console

Switch to using the unified mirage-console.2.0.0 package
Alias Console to Console_unix and Console_xen

This follows the changes in mirage/mirage-console#26
Merge pull request #305 from avsm/master

Alias Console to Console_unix and Console_xen
Merge pull request #300 from avsm/vchan-conduit

Add Vchan support to Mirage config.ml
Change some default paramater to be optional

warning: this will cause existing config.ml to certainly break