Update config.sub, config.guess and configure.in

Thanks to Stéphane Glondu.
Do not use -custom

Thanks to Stéphane Glondu.
Remove obsolete doc/makefiles.txt
Remove RELEASE switch and obsolete make targets
Improve META
Strip obsolete bits
Move aclocal.m4 to m4/cil.m4
Comply with safety-switch for If-Else autoconf macros

Introduced in autoconf 2.68.
Use ocaml-autoconf macros
Better automatic remaking
Remove Testcil and Testcilint modules
autoconf: remove ARCHOS, MINGW, DEFAULT_COMPILER
Remove more files

Removing TODO because it has not been updated in the last ten years.
None of it will ever be done unless someone fills new and precise
bug reports.

Removing unued Bootstrap and ocamlbuild's *.itarget as well.
Update install-sh
Build bytecode only if opt is not available
Remove unused test 'hola'
Remove unused Prettytest
Use ocamlbuild for compilation
Remove broken http link in doc
Use ocamlbuild for documentation

Do not build CIL-API.pdf anymore.