Before this commit, the version of OCaml was defined on the first line
of the VERSION file present at the top-level of the source tree.

This commit defines the version of OCaml in build-aux/ocaml_version.m4
as a series of macros defining each component of the version and
then putting all these components together in the right way to
obtain the main version string and the other variants used here and there.

With this commit, the VERSION file becomes a by-product of running autoocnf,
which is usually done by running tools/autogen.

However, this commit takes special care of generating the very same
VERSION file than the one used before the commit. The modifications
in the comments will be introduced in subsequent commits, for the
sake of clarity and to make it possible and eaiser to verify that
nothing has been broken or altered.

With this commit all the components of the version number become available
to the configure script which will thus be available to propagate them
to the whole build system.

…SION file

This means that, before this commit, runtime/caml/version.h was
generated during the build process by a recipe found in runtime/Makefile.

After this commit, runtime/caml/version.h is generated by the configure
script from runtime/caml/version.h.in

This commit makes an effort to guarantee that the version.h file
generated by configure is as similar as possible to the one produced
by the make recipe before, that's why runtime/caml/version.h.in
contains no copyright notice at this stage.
It will be added in the following commit.

At this stage, the only difference between the two versions of version.h
(the one generated by make before and the one generated by configure now)
is the coment line produced by configure as the first line of version.h, namely:

/* runtime/caml/version.h.  Generated from version.h.in by configure.  */

but this cannot be avoided and is harmless.

This is a shorter alias for OCAML_VERSION_ADDITIONAL

Before this commit a dedicated version.h file was generated.

More precisely, before this commit the AUTOCONF_FILES variable was listing
the VERSION file, which is no longer necessary. Nothing needs to be added because
the build-aux/* also matches build-aux/ocaml_version.m4 where the
version of OCaml is now defined.

This commit also increases the HOOK_VERSION variable from 5 to 6.

Make it po point to the right place where the version of OCaml is
actually defined.

This also required a modification of the root makefile so that its
clean and distclean targets also call the corresponding ones in
the manual.

…efile

This commit introduces the different components of an OCaml version
as build variables.

It thus becomes possible to test from within the build system whether
the currently built version of OCaml is a development version or not.

This ability is used to move the development version test from the
beginning of tools/check-parser-uptodate-or-warn.sh to the root Makefile,
which will make that test portable even to non-Posix systems and
no matter how the locales are configured.

…s module