added incremental extension functions: extend_log_types, extend_type_gram,
extend_const_gram, extend_consts, extend_trfuns, extend_trrules;
replaced merge by merge_syntaxes;
various minor internal changes;
BoolNat = Arith +
types bool,nat 0
arities bool,nat :: arith
consts Suc :: "nat=>nat"
rules add0 "0 + n = n::nat"
addS "Suc(m)+n = Suc(m+n)"
nat1 "1 = Suc(0)"
or0l "0 + x = x::bool"
or0r "x + 0 = x::bool"
or1l "1 + x = 1::bool"
or1r "x + 1 = 1::bool"
end