Attempt to complile Python/dynload_win.c by MinGW fails
due to static reimplementation of strcasecmp function in this file:

---
/* Case insensitive string compare, to avoid any dependencies on particular
   C RTL implementations */

static int strcasecmp (char *string1, char *string2)
{
    int first, second;

    do {
        first  = tolower(*string1);
        second = tolower(*string2);
        string1++;
        string2++;
    } while (first && first == second);

    return (first - second);
}
---

And this reimplementation clashed with native declaration of strcasecmp()
which one is a part of MinGW runtime

So suggested patch (for 3.5.2 and 2.7.12)
just disables static reimplementation of strcasecmp for MinGW