Remove the notion of "sys*"

- This idea originates from very early in the project and was, at the
  time, a very easy way to categorise things.
- Now, it doesn't really make much sense - it is fairly arbitary, often
  occuring when there is a change in kernel, but not from builder-hex0
  to fiwix, and sysb is in reality completely unnecessary.
- In short, the sys* stuff is a bit of a mess that makes the project
  more difficult to understand.
- This puts everything down into one folder and has a manifest file that
  is used to generate the build scripts on the fly rather than using
  coded scripts.
- This is created in the "seed" stage.

stage0-posix -- (calls) --> seed -- (generates) --> main steps

Alongside this change there are a variety of other smaller fixups to the
general structure of the live-bootstrap rootfs.

- Creating a rootfs has become much simpler and is defined as code in
  go.sh. The new structure, for an about-to-be booted system, is

/
-- /steps (direct copy of steps/)
-- /distfiles (direct copy of distfiles/)
-- all files from seed/*
-- all files from seed/stage0-posix/*

- There is no longer such a thing as /usr/include/musl, this didn't
  really make any sense, as musl is the final libc used. Rather, to
  separate musl and mes, we have /usr/include/mes, which is much easier
  to work with.
- This also makes mes easier to blow away later.
- A few things that weren't properly in packages have been changed;
  checksum-transcriber, simple-patch, kexec-fiwix have all been given
  fully qualified package names.
- Highly breaking change, scripts now exist in their package directory
  but NOT WITH THE packagename.sh. Rather, they use pass1.sh, pass2.sh,
  etc. This avoids manual definition of passes.
  - Ditto with patches; default directory is patches, but then any patch
    series specific to a pass are named patches-passX.

sysc/gcc-4.7.4/patches/remove_gperf_dependency.patch

@@ -1,36 +0,0 @@
-SPDX-FileCopyrightText: 2021 Andrius Štikonas <andrius@stikonas.eu>
-SPDX-License-Identifier: GPL-3.0-or-later
-
-Remove dependency on gperf.
-
---- gcc/cp/except.c	2021-07-07 18:24:36.561530121 +0100
-+++ gcc/cp/except.c	2021-07-07 18:27:18.035681929 +0100
-@@ -987,8 +987,6 @@
-    exception, unless it calls a program-supplied function that
-    throws an exception.  */
- 
--#include "cfns.h"
--
- int
- nothrow_libfn_p (const_tree fn)
- {
-@@ -1007,7 +1005,7 @@
-      unless the system headers are playing rename tricks, and if
-      they are, we don't want to be confused by them.  */
-   id = DECL_NAME (fn);
--  return !!libc_name_p (IDENTIFIER_POINTER (id), IDENTIFIER_LENGTH (id));
-+  return 0;
- }
- 
- /* Returns nonzero if an exception of type FROM will be caught by a
---- gcc/cp/Make-lang.in	2021-07-07 18:24:36.571530380 +0100
-+++ gcc/cp/Make-lang.in	2021-07-07 18:26:47.154887799 +0100
-@@ -313,7 +313,7 @@
- cp/rtti.o: cp/rtti.c $(CXX_TREE_H) $(TM_H) $(FLAGS_H) convert.h \
-   $(TARGET_H) $(C_PRAGMA_H) gt-cp-rtti.h intl.h
- cp/except.o: cp/except.c $(CXX_TREE_H) $(TM_H) $(FLAGS_H) \
--  cp/cfns.h $(TREE_INLINE_H) $(TARGET_H) gt-cp-except.h
-+  $(TREE_INLINE_H) $(TARGET_H) gt-cp-except.h
- cp/expr.o: cp/expr.c $(CXX_TREE_H) $(TM_H) $(FLAGS_H) $(TM_P_H)
- cp/pt.o: cp/pt.c $(CXX_TREE_H) $(TM_H) cp/decl.h cp/cp-objcp-common.h \
-   toplev.h $(TREE_INLINE_H) pointer-set.h gt-cp-pt.h vecprim.h intl.h \