[logic] In fact_ctx, use an indirection of expressionMM

It saves a lot of time in the processing of inference, because this
complex data structure is not copied anymore, but shared (in
proof_tree::compute_node_state). See comment in logic/engine.hh to see
why it is correct.
[cmake] Add the needed environment to run the different tests
[model] Fix handling of abort in compute_wait_expression

The issue is a fallout from a2a05e1dceb. We need to check about active
state, i.e (running or waiting), and not only running.
[test] Relax a bit the time on network_tcp timeout test

With 100ms, the test breaks reliably with boost-1.50, but works properly
on other plateform tested (1.46.1, 1.49, 1.54, ...). It does not change
the semantic of the test, so ...