added isactrlconst

--- a/lib/texinputs/isabelle.sty	Mon Oct 16 10:27:54 2006 +0200
+++ b/lib/texinputs/isabelle.sty	Mon Oct 16 14:07:18 2006 +0200
@@ -31,6 +31,7 @@
 \newcommand{\isactrlesup}{\egroup\egroup\end{math}\egroup}
 \newcommand{\isactrlbold}[1]{{\bfseries\upshape\boldmath#1}}
 \newcommand{\isactrlloc}[1]{{\bfseries\upshape\boldmath#1}}
+\newcommand{\isactrlconst}{}
 
 
 \newdimen\isa@parindent\newdimen\isa@parskip