Fix for Mantis 6221.

http://caml.inria.fr/mantis/view.php?id=6221

Test case:

    $ cat field.ml
    <:ctyp< a:b >>

Before:

    $ camlp4of field.ml
    File "field.ml", line 1, characters 10-11:
    While expanding quotation "ctyp" in a position of "str_item":
      Parse error: "->" expected after [ctyp level star] (in [ctyp])

After:

    $ camlp4of field.ml
    Ast.TyCol (_loc, (Ast.TyId (_loc, (Ast.IdLid (_loc, "a")))),
      (Ast.TyId (_loc, (Ast.IdLid (_loc, "b")))))
Merge pull request #40 from yallop/mantis-6221

Fix for Mantis 6221.
attempt at fixing #41
install with findlib
Travis: improve the script to install ocamlfind

Necessary from the shift to findlib installation in ade6468a2e6c202
Travis: correct OPAM_VERSION parsing
Fix installation by selecting META file from source tree, not _build
Fix install when only bytecode is compiled by making cmx optional

Also make installation idempotent by removing any previous install
that was around previously.
Travis: test both bytecode-only and bytecode+native installation
Travis: remove a BSD-ism that snuck in (gmake -> make)
Add an `opam` file to test uninstall/install as OPAM package will do
Travis: also attempt a reinstallation to check that upgrade will work
opam: remove the `.opt` versions of the camlp4 binaries as well
Merge pull request #43 from avsm/trunk

fix build and improve the Travis script to install ocamlfind
Changes --> CHANGES.md
Revert commits for installing camlp4 with ocamlfind
add the PaExc constructor

for `exception patt` in patterns.
bootstrap
support the `exception patt` syntax
bootstrap