added Syntax.const_abs_tr' with proper eta_abs and Term.is_dependent;
recovered printing of Hoare assign statements from 45d090186bbe;
\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|)}