load underscore package after iman etc.;

--- a/doc-src/System/system.tex	Mon Sep 15 16:43:53 2008 +0200
+++ b/doc-src/System/system.tex	Mon Sep 15 16:50:35 2008 +0200
@@ -9,9 +9,9 @@
 \usepackage{textcomp}
 \usepackage{supertabular}
 \let\intorig=\int  %iman.sty redefines \int
-\usepackage[nohyphen,strings]{../underscore}
 \usepackage{graphicx}
 \usepackage{../iman,../extra,../isar,../ttbox}
+\usepackage[nohyphen,strings]{../underscore}
 \usepackage{../isabelle,../isabellesym}
 \usepackage{../IsarRef/style}
 \usepackage{../pdfsetup}