fix repeated tagged-to-i deopt

the comp_pivot variables were occasionally being used before being initialized.
the tagged-to-i operation would bail because of NaN being introduced when they
were used.

Author: chrisdickinson

lib/compile_sort.js

@@ -230,9 +230,9 @@ function createQuickSort(order, dtype, insertionSort) {
     "ptr0",
     "ptr1",
     "ptr2",
-    "comp_pivot1",
-    "comp_pivot2",
-    "comp"
+    "comp_pivot1=0",
+    "comp_pivot2=0",
+    "comp=0"
   ]
 
   if(order.length > 1) {