patch 8.0.1572: Mac: getting memory size doesn't work everywhere

Problem:    Mac: getting memory size doesn't work everywhere.
Solution:   Use MACOS_X instead of MACOS_X_DARWIN. (Kazunobu Kuriyama)
diff --git a/src/version.c b/src/version.c
index 2f045e4..f1a3b95 100644
--- a/src/version.c
+++ b/src/version.c
@@ -767,6 +767,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1572,
+/**/
     1571,
 /**/
     1570,