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-gcc/hello-mes.S

@@ -0,0 +1,58 @@
+/*
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 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: */
+
+/* Using gdb, esp. GUD in GNU Emacs is recommended
+M-x gdb-display-disassembly-buffer
+M-x gdb-display-io-buffer
+set disassemble-next-line on
+break _start
+run
+info registers
+si
+p/x $rax
+RET
+...
+*/
+
+/** Code: */
+
+SYS_exit 	= 0x3c		/* Linux syscalls.  */
+SYS_write 	= 0x01
+stdout		= 1		/* File discriptor */
+	.globl _start		/* Magic linker symbol: --entry-address.  */
+
+	.text			/* Program text. */
+_start:
+	movabs	$SYS_write,%rax	/* System call function: write, in %rax.  */
+	movabs	$stdout,%rdi	/* 1st parameter: file descriptor, in %rdi. */
+	movabs	$hello,%rsi	/* 2nd parameter: address, in %rsi. */
+	movabs	$(bye-hello),%rdx	/* 3rd parameter: byte count %rdx. */
+	syscall			/* Call system.  */
+
+	movabs	$SYS_exit,%rax	/* System call function: exit, in %rax.  */
+	movabs	$0,%rdi		/* 1st parameter: exit status, in %rdi. */
+	syscall			/* Call system.  */
+	hlt 			/* Should not be reached.  */
+
+	.data
+hello:	.ascii	"Hello, GNU Mes!\n"
+bye:	.byte	0