patch 8.0.1568: can't build on older Mac, header file is missing

Problem:    Can't build on older Mac, header file is missing.
Solution:   Remove the header file. (Ozaki Kiichi, closes #2691)
diff --git a/src/os_unix.c b/src/os_unix.c
index 45fd261..9819176 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -566,7 +566,6 @@
 # ifdef MACOS_X_DARWIN
 #  include <mach/mach_host.h>
 #  include <mach/mach_port.h>
-#  include <mach/vm_page_size.h>
 # endif
 
 /*
diff --git a/src/version.c b/src/version.c
index cbd28ee..96ac824 100644
--- a/src/version.c
+++ b/src/version.c
@@ -767,6 +767,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1568,
+/**/
     1567,
 /**/
     1566,