Added function 'add_proved' and a fix

fix: The field 'entry' in the module 'Proof_context' has mutable
     subfields. I.e. if the 'entry' is stacked it has to be stacked
     as a copy. Otherwise the subfields of the stacked entry and the
     current entry will be modified.

	modified:   ocaml/context.ml
	modified:   ocaml/context.mli
	modified:   ocaml/proof_context.ml
	modified:   ocaml/proof_context.mli
	modified:   ocaml/proof_table.ml
	modified:   ocaml/proof_table.mli
	modified:   ocaml/term_table0.ml
Fix: 'Term.binary' put the left and right operand in the wrong order

	modified:   ocaml/term.ml
Fix: Some typos which led to wrong behaviour

	modified:   ocaml/proof_context.ml
	modified:   ocaml/term_table0.ml
Added draft version of the new prover

The new prover which is base on the modules 'Context', 'Proof_context'
and 'Proof_table' is not yet activated but added for test purposes.

	modified:   ocaml/context.ml
	modified:   ocaml/context.mli
	modified:   ocaml/proof_context.ml
	modified:   ocaml/proof_context.mli
	modified:   ocaml/proof_table.ml
	modified:   ocaml/proof_table.mli
	new file:   ocaml/prover2.ml
Fixed precedence of 'all' and 'some'

'all' and 'some' must have a higher precedence than '=>'.

	modified:   ocaml/support.ml
Fix: Bug in printing of anonymous variables

	modified:   ocaml/feature_table.ml
Improved readability of 'specialized_forward'

	modified:   ocaml/proof_context.ml
Fix: Update of type variable only if set

	modified:   ocaml/signature.ml
	modified:   ocaml/term.ml
Fix: Substitutions now applied in 'update_type_variables'

The type inference infers the type of untyped variables. But the
inferred types also have to be applied to the 'argtypes' in order
to be visible effective.

	modified:   ocaml/context.ml
	modified:   ocaml/signature.ml
	modified:   ocaml/term.ml
New prover tested with prover 'basic' on some examples

- Subproofs not yet implemented

- Iterated backward reasoning not yet implemented

	modified:   ocaml/context.ml
	modified:   ocaml/context.mli
	modified:   ocaml/parser.mly
	modified:   ocaml/proof_context.ml
	modified:   ocaml/proof_context.mli
	modified:   ocaml/proof_table.ml
	modified:   ocaml/proof_table.mli
	modified:   ocaml/prover2.ml
	modified:   ocaml/support.ml
	modified:   ocaml/term_table0.ml