Add Uint32AddWithOverflow and Uint32SubWithOverflow machine operators.

src/compiler/instruction-selector-impl.h

Index: src/compiler/instruction-selector-impl.h
diff --git a/src/compiler/instruction-selector-impl.h b/src/compiler/instruction-selector-impl.h
index 573c1ff41e46bbe7ee2d859c61bf7cc414351f84..24d397dce73d370c7d4a903fb7e3b06c9368fa88 100644
--- a/src/compiler/instruction-selector-impl.h
+++ b/src/compiler/instruction-selector-impl.h
@@ -270,8 +270,6 @@ class FlagsContinuation V8_FINAL {
     switch (condition_) {
       case kEqual:
       case kNotEqual:
-      case kOverflow:
-      case kNotOverflow:
         return;
       case kSignedLessThan:
         condition_ = kSignedGreaterThan;
@@ -312,6 +310,10 @@ class FlagsContinuation V8_FINAL {
       case kUnorderedGreaterThan:
         condition_ = kUnorderedLessThan;
         return;
+      case kOverflow:
+      case kNotOverflow:
+        // We cannot commute these.
+        break;
     }
     UNREACHABLE();
   }