Use CALLOC() instead of its pattern

MALLOC() + memset() is simpler written as CALLOC().

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/groupmem.c

@@ -23,12 +23,11 @@
 	struct group *gr;
 	int i;
 
-	gr = MALLOC(1, struct group);
+	gr = CALLOC(1, struct group);
 	if (NULL == gr) {
 		return NULL;
 	}
 	/* The libc might define other fields. They won't be copied. */
-	memset (gr, 0, sizeof *gr);
 	gr->gr_gid = grent->gr_gid;
 	/*@-mustfreeonly@*/
 	gr->gr_name = strdup (grent->gr_name);