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>

src/gpasswd.c

@@ -19,6 +19,8 @@
 #include <signal.h>
 #include <stdio.h>
 #include <sys/types.h>
+
+#include "alloc.h"
 #include "defines.h"
 #include "groupio.h"
 #include "nscd.h"
@@ -834,7 +836,7 @@ static void get_group (struct group *gr)
 
 			sg->sg_mem = dup_list (gr->gr_mem);
 
-			sg->sg_adm = (char **) xmallocarray (2, sizeof (char *));
+			sg->sg_adm = XMALLOCARRAY (2, char *);
 #ifdef FIRST_MEMBER_IS_ADMIN
 			if (sg->sg_mem[0]) {
 				sg->sg_adm[0] = xstrdup (sg->sg_mem[0]);