cleaned up system tag.

tests/testsystem.jet

@@ -1,8 +1,8 @@
 #!../jet-2.0
 <jet name1="localname" filterblanklines="true" trimlines="true">
 <set name="abc" value="abcdefg" />
-<system cmd="cat" status="stat" input="$[abc]xyz" name="test1" />
+<system cmd="cats" input="$[abc]xyz" name="test1" />
 test1=$[test1]
 name1=#[localname]
-status=$[stat]
+error=$[error]
 </jet>