patch 8.2.5071: with some Mac OS version clockid_t is redefined

Problem:    With some Mac OS version clockid_t is redefined.
Solution:   Adjust #ifdefs. (Ozaki Kiichi, closes #10549)
diff --git a/src/os_mac.h b/src/os_mac.h
index 646dff4..a7b1dba 100644
--- a/src/os_mac.h
+++ b/src/os_mac.h
@@ -272,15 +272,14 @@
 
 # include <dispatch/dispatch.h>
 
-# if !defined(MAC_OS_X_VERSION_10_12) || \
-	(MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_12)
+# ifndef MAC_OS_X_VERSION_10_12
 typedef int clockid_t;
 # endif
 # ifndef CLOCK_REALTIME
-#   define CLOCK_REALTIME 0
+#  define CLOCK_REALTIME 0
 # endif
 # ifndef CLOCK_MONOTONIC
-#   define CLOCK_MONOTONIC 1
+#  define CLOCK_MONOTONIC 1
 # endif
 
 struct itimerspec