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-mes/elf32-footer-single-main.hex2

@@ -0,0 +1,64 @@
+### Copyright (C) 2017 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+### This file is part of stage0.
+###
+### stage0 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.
+###
+### stage0 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 stage0.  If not, see <http://www.gnu.org/licenses/>.
+
+### stage0's hex2 format for x86
+###    !<label>          1 byte relative
+###    $<label>          2 byte address
+###    @<label>          2 byte relative
+###    &<label>          4 byte address
+###    %<label>          4 byte relative
+###    local_<label>     function-local
+###    string_<index>    string #<index>
+
+### elf32-footer-single-main.hex2: 32 bit elf footer in hex2 for single main
+
+# @230
+
+:ELF_str
+00                             # 0
+:ELF_str__start
+5f 73 74 61 72 74 00           # _start
+:ELF_str__main
+6d 61 69 6e 00                 # main
+
+00 00 00
+
+# @240
+:ELF_sym
+00 00 00 00                    # st-name
+00 00 00 00                    # st-offset: &_start - BaseAddress
+00 00 00 00                    # st-len   : &main - _start
+00                             # st-info = stt-func= 2
+00                             # st-other
+01 00                          # st-shndx: 1
+
+# _start
+%ELF_str__start>ELF_str        # st-name
+&_start
+10 00 00 00                    # st-len   : &main - _start
+02                             # st-info = stt-func= 2
+00                             # st-other
+01 00                          # st-shndx: 1
+
+# main
+%ELF_str__main>ELF_str         # st-name
+&main
+10 00 00 00                    # st-len   : &ELF_data - main
+02                             # st-info = stt-func= 2
+00                             # st-other
+01 00                          # st-shndx: 1
+
+:ELF_end