Removed 'Context' from the system and used 'Local_context' instead

	modified:   ocaml/eiffelc.ml
	modified:   ocaml/local_context.ml
	modified:   ocaml/local_context.mli
	modified:   ocaml/prover.ml
	modified:   ocaml/prover.mli
	modified:   ocaml/typer.ml
	deleted:    ocaml/context.ml