Add SCM_SECURITY, SCM_PIDFD to bits/socket.h

Linux 6.5 adds a constant SCM_PIDFD (recall that the non-uapi
linux/socket.h, where this constant is added, is in fact a header
providing many constants that are part of the kernel/userspace
interface).  This shows up that SCM_SECURITY, from the same set of
definitions and added in Linux 2.6.17, is also missing from glibc,
although glibc has the first two constants from this set, SCM_RIGHTS
and SCM_CREDENTIALS; add both missing constants to glibc.

Tested for x86_64.

sysdeps/unix/sysv/linux/bits/socket.h

@@ -367,6 +367,10 @@ enum
 #ifdef __USE_GNU
     , SCM_CREDENTIALS = 0x02	/* Credentials passing.  */
 # define SCM_CREDENTIALS SCM_CREDENTIALS
+    , SCM_SECURITY = 0x03	/* Security label.  */
+# define SCM_SECURITY SCM_SECURITY
+    , SCM_PIDFD = 0x04		/* Pidfd.  */
+# define SCM_PIDFD SCM_PIDFD
 #endif
   };