v1.3 release
The big change in this version is MSVC 2013 support. Sadly, mingw is unable to build MSVC-compatible dlls, as far as I've been able to figure out, so I've merged fanc999's patches for MSVC 2013 support.
Another big change is that OSX drops GLX support. I had had near-universal complaints about including it, and its seems like X on OSX is really not used these days (The lack of activity on its X server makes that pretty obvious).
Also included are the usual updates to the registry, fixes for a nonconformant GL implementation, some library size reductions, and reproducible builds.