String.fromCharCode.length, Math.max.length, Array.from.length
were returning 0 because their SX lambdas use &rest args with no
required params — but spec assigns each a specific length.
Added js-builtin-fn-length mapping JS name to spec length (12
entries). js-fn-length consults the table first and falls back to
counting real params.
built-ins/String: 79/99 → 80/99, built-ins/Array: 20/45 → 21/45.
conformance.sh: 148/148.
giles
0cfaeb9136