new file, implementation of elm messages command

+#include "config.h"
+#include <mailutils/mailutils.h>
+#include <stdio.h>
+#include <argp.h>
+
+const char *argp_program_version = "messages (" PACKAGE ") " VERSION;
+const char *argp_program_bug_address = "<bug-mailutils@gnu.org>";
+static char doc[] = "GNU messages -- count the number of messages in a mailbox";
+static char args_doc[] = "[mailbox...]";
+
+static struct argp_option options[] = {
+  { 0 }
+};
+
+struct arguments
+{
+  char **args;
+};
+
+static error_t
+parse_opt (int key, char *arg, struct argp_state *state)
+{
+  return 0;
+}
+
+static struct argp argp = { options, parse_opt, args_doc, doc };
+
+int
+main (int argc, char **argv)
+{
+  int i = 1;
+  list_t bookie;
+  mailbox_t mbox;
+  int count;
+  int err = 0;
+  struct arguments args;
+  args.args = NULL;
+
+  argp_parse (&argp, argc, argv, 0, 0, &args);
+
+  registrar_get_list (&bookie);
+  list_append (bookie, path_record);
+
+  /* FIXME: if argc < 2, check on $MAIL and exit */
+
+  for (i=1; i < argc; i++)
+    {
+      if (mailbox_create_default (&mbox, argv[i]) != 0)
+	{
+	  fprintf (stderr, "Couldn't create mailbox %s.\n", argv[i]);
+	  err = 1;
+	  continue;
+	}
+      if (mailbox_open (mbox, MU_STREAM_READ) != 0)
+	{
+	  fprintf (stderr, "Couldn't open mailbox %s.\n", argv[i]);
+	  err = 1;
+	  continue;
+	}
+      if (mailbox_messages_count (mbox, &count) != 0)
+	{
+	  fprintf (stderr, "Couldn't count messages in %s.\n", argv[i]);
+	  err = 1;
+	  continue;
+	}
+
+      printf ("Number of messages in %s: %d\n", argv[i], count);
+
+      if (mailbox_close (mbox) != 0)
+	{
+	  fprintf (stderr, "Couldn't close %s.\n", argv[i]);
+	  err = 1;
+	  continue;
+	}
+      mailbox_destroy (&mbox);
+    }
+  return 0;
+}