Fixed and improved code for integral division. Fixed and extended tests.

src/a64/lithium-a64.h

Index: src/a64/lithium-a64.h
diff --git a/src/a64/lithium-a64.h b/src/a64/lithium-a64.h
index 393b3e5f46f3864cd3c4bb16386e5118b977c3dd..33d11e6c5d8a9e3d14343d3c4c9ad0e24e07ed1f 100644
--- a/src/a64/lithium-a64.h
+++ b/src/a64/lithium-a64.h
@@ -1262,6 +1262,8 @@ class LDivI V8_FINAL : public LTemplateInstruction<1, 2, 1> {
   LOperand* right() { return inputs_[1]; }
   LOperand* temp() { return temps_[0]; }
 
+  bool is_flooring() { return hydrogen_value()->IsMathFloorOfDiv(); }
+
   DECLARE_CONCRETE_INSTRUCTION(DivI, "div-i")
   DECLARE_HYDROGEN_ACCESSOR(Div)
 };