All global tables now used exclusively via Context.t

	modified:   ocaml/context.ml
	modified:   ocaml/eiffelc.ml
	modified:   ocaml/prover.ml
	modified:   ocaml/prover.mli
	modified:   ocaml/support.ml
Some streamlining in the analysis of signatures

- function type eliminated
- formal generic names used consistently in some functions

	modified:   ocaml/class_table.ml
	modified:   ocaml/class_table.mli
	modified:   ocaml/context.ml
	modified:   ocaml/feature_table.ml
	modified:   ocaml/signature.ml