32-bit support for xxHash algorithm

[ghost]

Closes #1

[ekpyron]

Can you perhaps add a handful of canonical test cases to test.cpp? Then I'd be happy to merge this, thank you very much!

[ekpyron]

Suggested change

	return finalize( (len >= 16 ? h32bytes(p, len, seed) : seed+P5) + len, p+(len & ~0xF), len & 0xF );
	return finalize( (len >= 16 ? h16bytes(p, len, seed) : seed+P5) + len, p+(len & ~0xF), len & 0xF );

[ekpyron]

As a matter of fact, I just tried to extend the tests in test.cpp to your 32-bit implementation and checked against the reference implementation https://github.com/Cyan4973/xxHash/, but not all tests succeed, so there must be some small incorrectness in the implementation - I'll have a more detailed look later.

[ghost]

To be honest, it's been a long time since I wrote this and as far as I can remember, I didn't came into any problems when I used it. But anyway, I'll look at it soon and make any edits needed.

[ekpyron]

I'm just noticing that shockingly this has been open for a year now... I'll try looking into it soon, but I can't promise when I'll get around to.

[ghost]

Sorry for the force-push mess above, I initially committed with an old account name and wanted to get rid of it.

I forgot about this pull request but finally took the necessary time to finish it.
I added the tests to test.cpp as you requested and corrected my implementation to make them pass.

[ekpyron]

Nice! Thank you very much!