enable Z3 in the test configuration

--- a/Admin/mira.py	Thu Mar 24 17:56:59 2011 +0100
+++ b/Admin/mira.py	Thu Mar 24 22:12:38 2011 +0100
@@ -49,6 +49,7 @@
 ISABELLE_PATH="%s"
 
 ISABELLE_USEDIR_OPTIONS="$ISABELLE_USEDIR_OPTIONS %s -t true -v true -d pdf -g true -i true"
+Z3_NON_COMMERCIAL="yes"
 ''' % (isabelle_path, parallelism_options)
 
     writer = open(path.join(loc_isabelle, 'etc', 'settings'), 'a')