added delcongs, Delcongs, unsafe_solver, safe_solver, FOL_basic_ss,
safe_asm_more_full_simp_tac
new addss (old version retained as unsafe_addss),
new auto_tac (old version retained as unsafe_auto_tac),
clasimpset with modification functions
Bool = FOL +
types bool 0
arities bool :: term
consts tt,ff :: "bool"
end