isatest: indicate Isabelle version;

--- a/Admin/isatest/isatest-makeall	Fri Sep 24 15:30:30 2010 +0200
+++ b/Admin/isatest/isatest-makeall	Fri Sep 24 15:37:36 2010 +0200
@@ -146,6 +146,8 @@
 
     echo ------------------- starting test --- `date` --- $HOSTNAME > $TESTLOG 2>&1
 
+    echo "Isabelle version: $IDENT" >> $TESTLOG 2>&1
+
     if [ "${ISABELLE_HOME_USER:0:14}" == "/tmp/isabelle-" ]; then
         echo "--- cleaning up old $ISABELLE_HOME_USER"
         rm -rf $ISABELLE_HOME_USER