Added a second timeout mechanism to Refute.
For some reason, TimeLimit.timeLimit often does not work, and it
leaves Refute running forever, making any evaluation using
Mutabelle or Mirabelle impossible. The redundant timeout seems to
do the trick.
\index{model checking example|(}%
\index{lfp@{\texttt{lfp}}!applications of|see{CTL}}
\input{CTL/document/Base.tex}
\input{CTL/document/PDL.tex}
\input{CTL/document/CTL.tex}
\index{model checking example|)}