Make Unicorn buildable with MinGW (#1364)

* [WIN32] Allow to build also with MinGW

* [WIN32] Fix build for MinGW

qemu/util/qemu-error.c

@@ -44,7 +44,7 @@ static void error_print_loc(void)
  * Prepend the current location and append a newline.
  * It's wrong to call this in a QMP monitor.  Use qerror_report() there.
  */
-#ifdef _MSC_VER
+#ifdef _WIN32
 void error_vreport(const char *fmt, va_list ap)
 {
     error_print_loc();