Alien::TALib compiles under Cygwin but not Strawberry Perl
- Completing the exponential mov avg function
- updating movavg to barf on undefined N
- updating unit test to use perl code to test the PDL/TALib function for
  verification on systems that do not have or do not want to use TALib
- Removing barf from the movavg function. We don't barf and instead return null.
as the calling program can call barf or croak or whatever
Adding a unit test for expmovavg. works partially