twofish_test.go copyright

[keithbostic]

In the twofish_test.go file, there's the standard Go copyright, along with the comment:

        // These test are derived from http://www.schneier.com/code/ecb_ival.txt

and there's no copyright on that source file, so it's unclear the basis for the inclusion.

That might be worth clarifying.

[keithbostic]

Sorry, didn't realize it was a fork -- my apologies, I'll move.