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/linux/x86_64-mes/elf64-0exit-42.hex2

@@ -0,0 +1,36 @@
+### GNU Mes --- Maxwell Equations of Software
+### Copyright © 2017,2019 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/>.
+
+### Commentary:
+
+# elf64-exit-42.hex2: `exit 42' for x86_64-linux written in hex2
+# assembly, for usage with elf64-0header.hex2.  This produces a 160-byte
+# binary (a0 hex).  Inspiration was taken from GNU Gcc output of
+# exit-42.S.
+
+### Code:
+
+# @80
+:ELF_text
+48 b8 3c 00 00 00 00 00 00 00  # movabs $0x3c,%rax
+48 bf 2a 00 00 00 00 00 00 00  # movabs $42,%rdi
+0f 05                          # syscall
+f4                             # hlt
+
+00 00 00 00 00 00 00 00 00     # align to @a0
+:ELF_end