Bump to v4.12.0.

_stackClear.js

@@ -1,3 +1,5 @@
+var ListCache = require('./_ListCache');
+
 /**
  * Removes all key-value entries from the stack.
  *
@@ -6,7 +8,7 @@
  * @memberOf Stack
  */
 function stackClear() {
-  this.__data__ = { 'array': [], 'map': null };
+  this.__data__ = new ListCache;
 }
 
 module.exports = stackClear;