krb5 commit: Make IPv6 pktinfo work on macOS

https://github.com/krb5/krb5/commit/253e4459f4e4c9239e7a129bab4257f077d7bb94
commit 253e4459f4e4c9239e7a129bab4257f077d7bb94
Author: Greg Hudson <[email protected]>
Date:   Fri Dec 20 16:26:22 2019 -0500

    Make IPv6 pktinfo work on macOS
    
    Define __APPLE_USE_RFC_3542 to expose the definition of IPV6_PKTINFO
    on macOS.
    
    ticket: 8349

 src/lib/apputils/udppktinfo.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/src/lib/apputils/udppktinfo.c b/src/lib/apputils/udppktinfo.c
index c096c12..9a06ae8 100644
--- a/src/lib/apputils/udppktinfo.c
+++ b/src/lib/apputils/udppktinfo.c
@@ -23,6 +23,9 @@
  * or implied warranty.
  */
 
+/* macOS requires this define for IPV6_PKTINFO. */
+#define __APPLE_USE_RFC_3542
+
 #include "udppktinfo.h"
 
 #include <netinet/in.h>