make sure the module does what it says on the tin :-)

    fix the log-level functions e.g. trace(), debug() &c.

    these were previously hard-wired to always return 1,
    which meant that arguments were always evaluated and
    Log::Declare::log was always called; the log-level merely
    influenced whether the output should be printed.

    fixed (with tests) to ensure the expected short-circuiting behaviour