interactive use readline input. In batch mode, 'eval' interprets its
arguments as specs.

. adds an option that enable a command/response mode (for GUI
communication)
. adds an option to indicate a log file that receive all outputs of the
program (mainly for debuggin purpose)

stream is indicated either by an end-of-file character (e.g ^D) or by an
explicit keyword given as parameter (default=EOF).

"eval" command

did not check if the relations were computed or not.

. add a by-extension preprocessing mechanism. A default preprocessor can
  be defined.
. change preferences used to define preprocessors

Conflicts:
	configure.ac

. the same state was used for the src and the tgt of the transition
. the label of the transition was not unreferenced.

. adds utility scripts
. adds arc-ts2alt script that convert simple transition system into a node

the dependency graph.

dependency between transitions and assigned state variables.

. adds several options to display different kind of dependencies.

is observed. By default "visible" is used.

sequence computation.