prefer subarray over Array.prototype

src/runtime_init_memory.js

diff --git a/src/runtime_init_memory.js b/src/runtime_init_memory.js
index c5d3412..fc6bbf5 100644
--- a/src/runtime_init_memory.js
+++ b/src/runtime_init_memory.js
@@ -100,7 +100,7 @@
   if (!typedArray.prototype.slice) {
     Object.defineProperty(typedArray.prototype, 'slice', {
       value: function(begin, end) {
-        return new typedArray(Array.prototype.slice.call(this, begin, end));
+        return new typedArray(this.subarray(begin, end));
       }
     });
   }