'_PC_64' undeclared (first use in this function)

gistfile1.txt

add this code

```c
#ifndef _PC_64
#define _PC_64 0x00000000
#endif

#ifndef _MCW_PC
#define _MCW_PC 0x00030000
#endif
```

After

```c
#if defined(__MINGW64__)
/*
 * Use powl() instead of broken pow() of x86_64-w64-mingw32.
 * This workaround will fix test failures in test_bignum.rb,
 * test_fixnum.rb and test_float.rb etc.
 */
static inline double
rb_w32_pow(double x, double y)
{
    return powl(x, y);
}
#elif defined(__MINGW64_VERSION_MAJOR)
```

in the `<RUBY_INSTALL_PATH>\include\ruby-2.0.0\ruby\win32.h` fixes the problem.