Use safer allocation macros

Use of these macros, apart from the benefits mentioned in the commit
that adds the macros, has some other good side effects:

-  Consistency in getting the size of the object from sizeof(type),
   instead of a mix of sizeof(type) sometimes and sizeof(*p) other
   times.

-  More readable code: no casts, and no sizeof(), so also shorter lines
   that we don't need to cut.

-  Consistency in using array allocation calls for allocations of arrays
   of objects, even when the object size is 1.

Cc: Valentin V. Bartenev <vbartenev@gmail.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

lib/shadowmem.c

@@ -16,13 +16,15 @@
 #include "defines.h"
 #include <shadow.h>
 #include <stdio.h>
+
+#include "alloc.h"
 #include "shadowio.h"
 
 /*@null@*/ /*@only@*/struct spwd *__spw_dup (const struct spwd *spent)
 {
 	struct spwd *sp;
 
-	sp = (struct spwd *) calloc (1, sizeof *sp);
+	sp = CALLOC (1, struct spwd);
 	if (NULL == sp) {
 		return NULL;
 	}