fix(lib/runnable.js): Fix timeout range issue for good

Found that previous "fix" hadn't actually fixed the correct value, as the wrong upper bound value
had been used. Further checks indicated that IE had problems (surprise, surprise) with negative
timeout values. New code clamps to nonnegative range ending at `INT_MAX`.

Closes mochajs#1652

lib/runnable.js

@@ -60,10 +60,12 @@ utils.inherits(Runnable, EventEmitter);
  * Set timeout threshold value (msecs).
  *
  * @description
- * A string argument can use shorthand (such as "2s") and will be converted.
- * If value is `0` or exceeds `2^<sup>31</sup>-1`, timeouts will be disabled.
+ * A string argument can use shorthand (e.g., "2s") and will be converted.
+ * The value will be clamped to range [<code>0</code>, <code>2^<sup>31</sup>-1</code>].
+ * If clamped value matches either range endpoint, timeouts will be disabled.
  *
  * @private
+ * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/setTimeout#Maximum_delay_value}
  * @param {number|string} ms - Timeout threshold value.
  * @returns {Runnable} this
  * @chainable
@@ -75,8 +77,14 @@ Runnable.prototype.timeout = function(ms) {
   if (typeof ms === 'string') {
     ms = milliseconds(ms);
   }
+
+  // Clamp to range
+  var INT_MAX = Math.pow(2, 31) - 1;
+  var range = [0, INT_MAX];
+  ms = utils.clamp(ms, range);
+
   // see #1652 for reasoning
-  if (ms === 0 || ms > Math.pow(2, 31) - 1) {
+  if (ms === range[0] || ms === range[1]) {
     this._enableTimeouts = false;
   }
   debug('timeout %d', ms);