Fixed quantified variable name preservation for ball and bex (bounded quants)
Requires tweaking of other scripts. Also routine tidying.
primrec
"evala env (IF b a1 a2) =
(if evalb env b then evala env a1 else evala env a2)"
"evala env (Sum a1 a2) = evala env a1 + evala env a2"
"evala env (Diff a1 a2) = evala env a1 - evala env a2"
"evala env (Var v) = env v"
"evala env (Num n) = n"