Register names corrected
configure system: Many autohell errors fixed

* Most changes are due to the following autoconf issue:
http://www.gnu.org/software/autoconf/manual/autoconf.html#Expanded-Before-Required

  It doesn't say in a way a human would understand it, but apparently you
  can't have AC_PROG_CC in a macro. AC_REQUIRE it inside the macro doesn't
  help. The only choice I saw was to lift it out of the macros using it and
  expand it once before outside. Unfortunately this means many small changes
  in all configure.in files.

* BUILDCHAIN_MUARCH fixed stray temp solution. Use configured (auto-detected
  via configure) path to multi-arch target includes and libs (libc).

* Build configured to run hosted or not can now be picked up in compile
  time from the configuration. Especially certain machine-instructions that
  need privileged mode can't execute in hosted mode and need to be
  remarked. We might want to refine this further via command-line options as
  there could be cases were you both could and would provided that you can
  run as root. For now this is used only to enable/disable ability to
  CLI/STI.

* Many minor changes, spelling-/grammar-fixes mainly, but that make a
  difference as these are the help-text seen either when invoking
  './congfigure --help' or in the comments in ./include/tinker/config.h
  which is a public file meant to help the code who uses TinKer either, or
  both, in compile- and run-time.
Released  configuration option requirement

We're now able to configure and build a inner core of the kernel without any
additional ./configure option support. For a more competent hosted setup
under 64_x86:

./configure \
   --enable-verbose-config \
   --enable-pthread \
   --enable-posix_rt \
   --enable-max_threads=1000 \
   --enable-that_prio=1000 \
   --enable-max_prio=16 \
   --enable-min_stack=0x2400 \
   --enable-norm_stack=0x4800
-DARCH=$(ARCH) for native builds changed [IMPORTANT]

This change is flagged [IMPORTANT] as it might have future impact which I
can't foresee right now.

Used to be -DARCH=_$(ARCH), not sure if this was a typo or an intentional
"reminder to self" for some reason. It was a very long time since hosted
tinker builds were executing.

Remark:
=======
It would be better if as many defines got passed via
./include/tinker/configure instead, but for legacy and backwards
comparability to non-GNU tool-chains it seems some -D are still passed this
way. But GNU has it's own set of make-files so it seems somewhat redundant.

The only relevant reason for having macros passed via -D is when to resolve
path-names to include-files with more macros. But configure.h is in a
well-known hard-coded place (relative) place so it should be possible to
remove at least some -Dxxx macros. BOARD and MCPU might be different, but
even here I'm uncertain of if the  build-system wont allow you to configure
with one BORD/MCPU and build with another, or if that would even be
desirable.

Remaining issues:
* As the configure system ban be 1) tricked by the build system, 2)
  vice versa and 3) since many macros have #ifndef macro fall-backs, we
  should have a runt-time query API with some of the more important
  build/configure settings returned in a static struct.
Configure system: make.subdirs files removed

Dependency to "make.subdirs" removed as it's only confusing when one
build-system is used to configure another and what to configure is hidden in
yet another obscure file. When adding new platforms there will be a caos of
what is where and just because some parts in the build-system works doesn't
have to mean corresponding parts in the configure system works. *Too much*
flexibility can be counterproductive i.e.

The purpose of having those files in the first place were to help close down
parts of the tree where the configure-system was either broken or under
development. This feature still exists, but a better way to handle it would
be by using branches in the SCM and not merge on main until at both
build/configure works.

However to deploy the old feature: Just add a file "make.subdirs" in a
subdirectory and those directories will be pre-configured with "make
configure". This is really just a build-system boot-strap to create a
recursive set of configure scripts.  The real configuration is done with the
produced ./configure script, at any level even though it's recommended to
start from the root-level.
x86_64: Hosted exec has default configure vales

 Need to specify default components and component tuning parameters any
 longer. The configure-/build-system will now choose a fair (but
 x86-64-hosted specific) setting.
x86_64 hosted: Adding an empty board file

Satisfies the linker and kernel in hosted execution should (in theory) now
work. I.e. no need to add special linker-scripts nor crt0-files. ~10
years since last firing up in this mode, lets see how much is broken.

TinKer used to have stub-functions to emulate the most important things
(time e.t.a.). All rest except the components built is borrowed from the
host (in host mode).

Note amended
============
Following symbols remain unresolved (nowhere in any lib):

tk_bsp_sysinit
tk_pthread_sched
tk_pthread_sched_destruct
tk_pthread_sync
tk_pthread_sync_destruct
tk_root

Explicitly configure --disable-pthread --disable-posix_rt
Will lower unresolved symbols to:

tk_bsp_sysinit
tk_root

Satisfying these dependencies is easy but should not have been needed.
Host mode boot stub fix

We can't use macros to (void(0)) any longer since _b_hook expects a symbol
as in-argument. We're still trying to keeping the syntax non compiler
specific.
Jump-based context-switch

Lots of unrelated warnings and minor issues also cleared.

** Does not run **

Segfaults in the middle of setjmp.