Reland: Introduce a V8_NORETURN macro and use it to make GCC 4.9.2 happy again.

test/cctest/interpreter/test-bytecode-generator.cc

Index: test/cctest/interpreter/test-bytecode-generator.cc
diff --git a/test/cctest/interpreter/test-bytecode-generator.cc b/test/cctest/interpreter/test-bytecode-generator.cc
index 142fc5922fe934adce959f678b700956b734dd88..4b1b9d9b1d380f6fd8f37de7f4edd1b4b72185b9 100644
--- a/test/cctest/interpreter/test-bytecode-generator.cc
+++ b/test/cctest/interpreter/test-bytecode-generator.cc
@@ -169,6 +169,7 @@ static void CheckBytecodeArrayEqual(struct ExpectedSnippet<T> expected,
       switch (Bytecodes::SizeOfOperand(operand_type)) {
         case OperandSize::kNone:
           UNREACHABLE();
+          return;
         case OperandSize::kByte:
           expected_operand =
               static_cast<uint32_t>(expected.bytecode[operand_index]);
@@ -177,6 +178,9 @@ static void CheckBytecodeArrayEqual(struct ExpectedSnippet<T> expected,
           expected_operand = Bytecodes::ShortOperandFromBytes(
               &expected.bytecode[operand_index]);
           break;
+        default:
+          UNREACHABLE();
+          return;
       }
       if (raw_operand != expected_operand) {
         std::ostringstream stream;