tools: update ocamlfind handling

tools: update ocamlfind handling

configure checks just for ocamlc, but the tools in tools/ocaml depend
also on ocamlfind. On my workstation I have just ocamlc installed, but
no ocamlfind. As a result make will fail.

Update configure.ac to check also for OCAMLFIND, update various
Makefiles and replace hardcoded ocamlfind string with $(OCAMLFIND)

Please rerun autogen.sh after applying this patch.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>