Heavy work on while tag. Still needs work.

tests/testwhile.jet

@@ -0,0 +1,9 @@
+#!../jet-2.0
+<jet cgi="false" name1="localname" filterblanklines="true" trimlines="true">
+ <set name="ix" value="1" />
+ <while expr="$[ix]<10">
+  <set name="check" expr="$[ix]<10" />
+  -->$[check]-$[ix]<--
+  <set name="ix" expr="$[ix]+1" />
+ </while>
+</jet>