Update WIN32 ifdef checks to _MSC_VER

[harryr0se]

These code paths are wrapped with windows platform #ifdef checks but appear to be more specific to the compiler
Making these changes means I can compile with both MSVC and GCC (via MinGW) on Windows

Also just want to check, does us skipping this buffer clearing step on other compilers cause any issues?
I don't have a good idea of the lifetime of the error_strbuf object

// Make sure our buffer is empty
#ifdef _MSC_VER
    _Tidy();
#endif

[JBenda]

Good catch, thanks for fixing it.

The _Tidy() has no implications for executing it under normal circumstances.

I need to dig in again, I think it was some platform specific magic