sizeof.h: Move sizeof()-related macros to their own header

Cc: Christian Göttsche <cgzones@googlemail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

src/login_nopam.c

@@ -56,6 +56,8 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>		/* for inet_ntoa() */
 
+#include "sizeof.h"
+
 #if !defined(MAXHOSTNAMELEN) || (MAXHOSTNAMELEN < 64)
 #undef MAXHOSTNAMELEN
 #define MAXHOSTNAMELEN 256