import wasysym needed by Rewrite.thy

--- a/src/HOL/Probability/document/root.tex	Tue Jun 07 15:12:27 2016 +0200
+++ b/src/HOL/Probability/document/root.tex	Tue Jun 07 17:16:24 2016 +0200
@@ -2,6 +2,7 @@
 \usepackage{graphicx,isabelle,isabellesym,latexsym,textcomp}
 \usepackage{amsmath}
 \usepackage{amssymb}
+\usepackage{wasysym}
 \usepackage[only,bigsqcap]{stmaryrd}
 \usepackage[utf8]{inputenc}
 \usepackage{pdfsetup}