jolt-unc{add,sub,mul,inc,dec,neg}2 wrapped every non-flonum result to a
signed 64-bit integer, so (unchecked-add 2/3 2/3) truncated to 1 instead
of 4/3. Under *unchecked-math* the analyzer rewrites +/-/* to unchecked-*,
so any ratio arithmetic in such a file silently floored. Clojure's
unchecked-add falls back to regular arithmetic for non-primitives; only
long math wraps. Wrap iff both operands are exact integers.
Shaken out by test.check's gen/ratio monoid property (the + and 0 monoid
held for small-integers but failed for ratios).