PHPC-741: Fix variable reference in UTCDateTime init on Windows

Author: jmikola

src/BSON/UTCDateTime.c

@@ -71,7 +71,7 @@ static bool php_phongo_utcdatetime_init_from_string(php_phongo_utcdatetime_t *in
 	errno = 0;
 
 #if defined(PHP_WIN32)
-	milliseconds = _atoi64(s);
+	milliseconds = _atoi64(s_milliseconds);
 #else
 	milliseconds = bson_ascii_strtoll(s_milliseconds, &endptr, 10);
 #endif