Added MSVC 2013 support; Proper check of CPU's AVX2 feature support

[zenden2k]

Added Visual Studio solution. Tests passed. Could not run AVX2 test on unix because VirtualBox has no support for AVX instructions.

windows:

AVX2    encode  2252.10 MB/sec
AVX2    decode  3267.33 MB/sec
plain   encode  617.23 MB/sec
plain   decode  672.57 MB/sec
SSSE3   encode  2010.86 MB/sec
SSSE3   decode  2603.15 MB/sec

linux (vb):

plain   encode  1626.93 MB/sec
plain   decode  1469.71 MB/sec
SSSE3   encode  2203.48 MB/sec
SSSE3   decode  2683.54 MB/sec

[aklomp]

Hi, thanks for contributing! I tested the AVX2 support under Linux on a CPU with hardware support and it passes fine.

So, Windows support, eh :) I'm willing to work with you to integrate support for MSVC, but since I don't run Windows and have never worked with MSVC, I can't really update or test the MSVC code myself. Such "black box" code which the author cannot verify may be a problem if/when this library is extended in the future. But I don't think that outweighs the benefits of wider platform support.

I've taken a quick look at your pull request, and though it looks functionally OK, there are some issues that prevent me from merging it as-is. One of them is that all changes are rolled into one big commit. Would it be possible to split the commits up into smaller chunks like this:

• A commit that only changes the boolean operators in the encoders/decoders;
• A commit that only changes the AVX2 checks (with Windows support behind a #define);
• A commit that only changes the test suite to work with Windows;
• Finally, a commit that adds the MSVC build files.

That would make it easier to review the changes and isolate the locations which need porting work whenever the library changes.

Then there are some clarity/stylistic issues, which I will add as notes into your pull request. That might take me some time (over the weekend), though.

[aklomp]

Hey, are you still interested in contributing an MSVC port? Most of the setup work is in place now.

[zenden2k]

Yes is just am thinking about using CMake instead of Visual Studio soluition.

[aklomp]

Interesting! I wish I could help, but I don't have any experience with CMake. I like the idea though.