A more correct mapPar.  And tests.  (And a fixed test function)

You run this thing by doing, e.g.:

`% js -f Prototype.js -f Test.js -f TestMap.js`

I refactored the structure slightly to allow easy sharing of Util.js between the different test files.  I really don't have very much justification (as opposed to the option of passing Util.js on the command line above) beyond "this is temporary code anyway".