How-to make packages for 2.16

Hi,

The last release (2.16) has changed its default "make install" rule to
install through ocamlfind. This offers a standard META, a standard
ocamlfind support and a simple "uninstall" rule. It also makes
packaging simple but ocamlfind requires a couple of environment
variables that are hard to guess.

The next 4 lines are taken from the slackware build script; $PKG is
the directory which will be used for DESTDIR.

  OCAMLPATH="$PKG/usr/lib${LIBDIRSUFFIX}/ocaml"
  mkdir -p "$OCAMLPATH/stublibs"
  # Do *NOT* install in parallel.
  OCAMLFIND_DESTDIR="$OCAMLPATH" OCAMLPATH="$OCAMLPATH" DESTDIR="$PKG"
make -j1 install

Debian and Fedora do roughly the same. Do not hesitate to improve on
that if there is something wrong.

Also, if you haven't already done so, please read the README and
CHANGES files again: a _lot_ has been changed there.

Regards,
Adrien Nader