Add mes and mescc-tools-extra

mescc-tools-extra contains two important tools:
- cp
- chmod

mes first builds itself from a mes 0.21 seed as used by guix, and then
builds a mes 0.22 and then mes 0.22 using that created mes 0.22.

It does /not/ use bootstrap.sh as we don't have a proper shell at this
point, it has been manually adapted for kaem.

sysa/mes-0.22/lib/tests/scaffold/23-pointer.c

@@ -0,0 +1,69 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2017,2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+char *g_hello = "hello";
+char g_arena[4] = "XXX";
+char *g_chars = g_arena;
+
+int
+main ()
+{
+  if (*g_hello != 'h')
+    return 1;
+  if (g_hello[0] != 'h')
+    return 2;
+  if (g_chars[0] != 'X')
+    return 3;
+  if (*g_chars != 'X')
+    return 4;
+
+  g_arena[0] = 'A';
+  if (*g_chars != 'A')
+    return 5;
+  char *x = g_arena;
+  if (*x++ != 'A')
+    return 5;
+  *x++ = 'C';
+  if (g_chars[1] != 'C')
+    return 7;
+  if (g_chars[2] != 'X')
+    return 8;
+  *--x = 'X';
+  if (g_chars[1] != 'X')
+    return 9;
+
+  char **pp = &x;
+  if (**pp != 'X')
+    return 10;
+
+  char *p = *pp;
+  if (*p != 'X')
+    return 11;
+
+  char ***ppp = &pp;
+  if (***ppp != 'X')
+    return 12;
+
+  char **pp2 = *ppp;
+  if (**pp2 != 'X')
+    return 13;
+
+  return 0;
+}