Fix hb-private.hh compile issue

src/hb-private.hh

@@ -355,7 +355,7 @@ _hb_bit_storage (unsigned int number)
 {
 #if defined(__GNUC__) && (__GNUC__ >= 4) && defined(__OPTIMIZE__)
   return likely (number) ? (sizeof (unsigned int) * 8 - __builtin_clz (number)) : 0;
-#elif defined_MSC_VER) && defined(__OPTIMIZE__)
+#elif defined(_MSC_VER) && defined(__OPTIMIZE__)
   unsigned long where;
   if (_BitScanReverse(&where, number)) return 1 + where;
   return 0;
@@ -375,7 +375,7 @@ _hb_ctz (unsigned int number)
 {
 #if defined(__GNUC__) && (__GNUC__ >= 4) && defined(__OPTIMIZE__)
   return likely (number) ? __builtin_ctz (number) : 0;
-#elif defined_MSC_VER) && defined(__OPTIMIZE__)
+#elif defined(_MSC_VER) && defined(__OPTIMIZE__)
   unsigned long where;
   if (_BitScanForward(&where, n)) return where;
   return 0;