Do not print (get-info :reason-unknown) on smt2 output. Previously,
detection of end of model and beginning of statistics was done by using
the reason. We now detect a single parenthesis on a line: every cvc4 model
ends with this (we assume statistics does not contain a line beginning
with a closing parenthesis). As a side effect, we also find
more counterexamples.

* src/driver/parse_smtv2_model.ml
(parse): Revert changes that were detecting Abort trap.

* src/driver/parse_smtv2_model_parser.mly
(output): Revert changes to allow absence of parenthesis at the end. Also
removed parsing on results given by the reason. Now match on ).

* src/printer/smtv2_cvc_ce.ml
(print_prop_decl): Remove (get-info :reason-unknown).

* src/printer/smtv2.ml
(print_prop_decl): Remove get-info for coherence.

Change-Id: Ifbd7b2b9ce499f8aaa020f58375d784793990965