Move internal modules to “internal” folder.

.internal/hashClear.js

@@ -0,0 +1,15 @@
+import nativeCreate from './.internal/nativeCreate.js';
+
+/**
+ * Removes all key-value entries from the hash.
+ *
+ * @private
+ * @name clear
+ * @memberOf Hash
+ */
+function hashClear() {
+  this.__data__ = nativeCreate ? nativeCreate(null) : {};
+  this.size = 0;
+}
+
+export default hashClear;