configure.ml fixed wrt Win32 + byte-only + coqide
Spawn: managed processes

The Spawn and Spawned modules factor the operation of spawning
a process.  Both synchronous and asynchronous channels are supported.
Both threaded and glib like main loop models are supported.  Still,
not all combinations are truly tested not equipped with a decent API:
only async + glib and sync + thread are, since these are the models we
use for coqide<->coqtop and coqtop<->worker respectively.
CoqIDE: ported to spawn
STM: ported to spawn
break > 80 cols line
CoqIDE: command line for extra coqtop "flags"

Like the socket for the OCaml debugger
-schedule-vi-checking ported to spawn
Coercions: avoid imperative data structure