calloc: Make sure we always have an overflow-checking calloc() available

This tries to make sure that everywhere in this source tree, we always have
an appropriate version of calloc() (i.e. grub_calloc(), xcalloc(), etc.)
available, and that they all safely check for overflow and return NULL when
it would occur.

Signed-off-by: Peter Jones <pjones@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/kern/emu/mm.c

@@ -25,6 +25,16 @@
 #include <string.h>
 #include <grub/i18n.h>
 
+void *
+grub_calloc (grub_size_t nmemb, grub_size_t size)
+{
+  void *ret;
+  ret = calloc (nmemb, size);
+  if (!ret)
+    grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("out of memory"));
+  return ret;
+}
+
 void *
 grub_malloc (grub_size_t size)
 {