[wasm] Refactor encoder.h to use a proper buffer and remove OldFunctions section.

test/cctest/wasm/wasm-run-utils.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WASM_RUN_UTILS_H
 #define WASM_RUN_UTILS_H
 
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
@@ skipping 161 matching lines @@
     rng.NextBytes(raw, end - raw);
   }
 
   uint32_t AddFunction(FunctionSig* sig, Handle<Code> code) {
     if (module->functions.size() == 0) {
       // TODO(titzer): Reserving space here to avoid the underlying WasmFunction
       // structs from moving.
       module_.functions.reserve(kMaxFunctions);
     }
     uint32_t index = static_cast<uint32_t>(module->functions.size());
-    module_.functions.push_back({sig, index, 0, 0, 0, 0, 0, false});
+    module_.functions.push_back({sig, index, 0, 0, 0, 0, 0});
     instance->function_code.push_back(code);
     if (interpreter_) {
       const WasmFunction* function = &module->functions.back();
       int interpreter_index = interpreter_->AddFunctionForTesting(function);
       CHECK_EQ(index, static_cast<uint32_t>(interpreter_index));
     }
     DCHECK_LT(index, kMaxFunctions);  // limited for testing.
     return index;
   }
 
@@ skipping 569 matching lines @@
 // interpreter.
 #define WASM_EXEC_TEST(name)                                               \
   void RunWasm_##name(WasmExecutionMode execution_mode);                   \
   TEST(RunWasmCompiled_##name) { RunWasm_##name(kExecuteCompiled); }       \
   TEST(RunWasmInterpreted_##name) { RunWasm_##name(kExecuteInterpreted); } \
   void RunWasm_##name(WasmExecutionMode execution_mode)
 
 }  // namespace
 
 #endif