Also mention evaluable in list of expression variabilities (#3791)

Author: HansOlsson

chapters/operatorsandexpressions.tex

@@ -1503,10 +1503,12 @@ \section{Variability of Expressions}\label{variability-of-expressions}
 The concept of \firstuse[expression variability]{variability of an expression}\index{variability!expression|see{expression variability}} indicates to what extent the expression can vary over time.
 See also \cref{component-variability} regarding the concept of variability.
 % It seems wrong to not mention 'clocked discrete-time' here.
-There are four levels of variability of expressions, starting from the least variable:
+There are five levels of variability of expressions, starting from the least variable:
 \begin{itemize}
 \item
   constant variability
+\item
+  evaluable variability
 \item
   parameter variability
 \item