Parsing a model returned by the solver -  added possibility to specify the parser of model in the driver.

to branches in if statement.

since it is not interpreted as infinite by CVC4

As a side effect, this puts symbolic links back inside the archive. They
had been lost since 0.82 and prevented the use of a local installation.

It is now done by a different mechanism than parsing of time:
timeregexp is not any more used for parsing of steps, stepsregexp is
used instead.

- Switch from AUFNIRA to AUFBVNIRA logic in cvc4_bare

This commit also removes the laziness for accessing symbols, since they
are already in the scope at the time the plugin is loaded.