Change comparison: MAX_INT fits in an int

Not sure how we ended up with the '-1' everywhere.

src/core/common.h

@@ -86,7 +86,7 @@ template <typename T1, typename T2, typename T3> struct hash<tuple<T1, T2, T3>>
 namespace pyston {
 template <typename T>
 constexpr bool fitsInto(int64_t x) {
-    return std::numeric_limits<T>::min() <= x && x < std::numeric_limits<T>::max();
+    return std::numeric_limits<T>::min() <= x && x <= std::numeric_limits<T>::max();
 }
 }