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/groups.c

@@ -14,9 +14,12 @@
 #include <grp.h>
 #include <pwd.h>
 #include <stdio.h>
+
+#include "alloc.h"
 #include "defines.h"
 #include "prototypes.h"
 #include "shadowlog.h"
+
 /*
  * Global variables
  */
@@ -88,7 +91,7 @@ int main (int argc, char **argv)
 	GETGROUPS_T *groups;
 
 	sys_ngroups = sysconf (_SC_NGROUPS_MAX);
-	groups = (GETGROUPS_T *) mallocarray (sys_ngroups, sizeof (GETGROUPS_T));
+	groups = MALLOCARRAY (sys_ngroups, GETGROUPS_T);
 
 	(void) setlocale (LC_ALL, "");
 	(void) bindtextdomain (PACKAGE, LOCALEDIR);