MinGW not properly checked for in macros.

[MakoEnergy]

I am here due to some difficulties trying to get Bullet3 up and running on MinGW. In Macros.h windows is checked for using "_WIN32" and then uses non-portable versions of functions (vsnprintf_s, for example) available only in MSVC. This is a problem since MSVC isn't the only compiler available on Windows.

The
#ifdef _WIN32
should be replaced with
#ifdef _MSC_VER
if the intent is to use MSVC specific features.

The
#elif defined(__linux__)
should also probably be replaced with
#elif defined(__linux__) || defined(__GNUC__).

In the case of MinGW, the __GNUC__ would be detected and used.