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>

lib/idmapping.c

@@ -21,6 +21,7 @@
 #include <sys/capability.h>
 #endif
 #include "shadowlog.h"
+#include "sizeof.h"
 
 struct map_range *get_map_ranges(int ranges, int argc, char **argv)
 {