Licensing of Windows test functions taken from Ruby source

[maxirmx]

Windows version of libdwarfs uses for tests functions taken from original Ruby source.
This code is now placed in disorder to a single file: rb_w32-tebako-tests-mocks.c

In the original Ruby source the code that I took is tagged partially with

/* License: Ruby's */

and partially with

/* License: Artistic or GPL */

Shall we add anything to our license ? Adopted code is used to testing only.

[ronaldtse]

I think it’s fine to keep the tests, and we have to describe the licenses properly. However, we must not distribute the tests with the gem.

To that, let’s add a test so that we don’t distribute these tests.