[conformal/btcscript] f529a3: Add tests for doing math on 5-byte ints.

[Dave Collins]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcscript
  Commit: f529a37123efa587f90c1147c4d847fcd077b5ab
      
https://github.com/conformal/btcscript/commit/f529a37123efa587f90c1147c4d847fcd077b5ab
  Author: Dave Collins <da...@conformal.com>
  Date:   2014-04-03 (Thu, 03 Apr 2014)

  Changed paths:
    M data/script_invalid.json
    M test_coverage.txt

  Log Message:
  -----------
  Add tests for doing math on 5-byte ints.

This commit addes a couple of tests to ensure performing math operations
on a 5-byte integer, even if the result is a 4-byte integer, is considered
invalid.