build: replace ocamlcomp*.sh.

This script was built from ocamlcomp.sh.in through sed and is called
instead of "ocamlc" (for instance).
It makes it possible to switch from "ocamlc" to "ocamlc.opt" without
changing anything in the Makefiles, only calling sed.

I couldn't cleanly make it handle both a compiler for the target and for
the build. Instead I'm replacing it and doing as much as possible
directly in the Makefiles.
I hoped it would reduce the number of shell invocations, which would
speed things up quite a lot on Windows but I still had to have at least
one since it's not possible to update a make variable from inside a make
rule: i.e. it's not possible to do X=a, build a.opt and update X to be
a.opt.

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14168 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
build: remove warning 32 (unused variable) in tools.

(Patch by Adrien Nader!)

Among other files, myocamlbuild_config.ml is built in this directory.
This file defines many variables, most of which are not used and
therefore trigger this warning which is then turned into an error
through -warn-error A.
build: remove warning 32 (unused variable) in tools.

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14169 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02