Moved zones and zone related stuff in its own directory.

test/fuzzer/wasm-code.cc

Index: test/fuzzer/wasm-code.cc
diff --git a/test/fuzzer/wasm-code.cc b/test/fuzzer/wasm-code.cc
index 0307322a406511ae3e54696c11f241f392e8aa72..feb3e24618f8975cafa7d1ce5bbf7a0971cb28e8 100644
--- a/test/fuzzer/wasm-code.cc
+++ b/test/fuzzer/wasm-code.cc
@@ -32,7 +32,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   v8::Context::Scope context_scope(support->GetContext());
   v8::TryCatch try_catch(isolate);
 
-  v8::base::AccountingAllocator allocator;
+  v8::internal::AccountingAllocator allocator;
   v8::internal::Zone zone(&allocator);
 
   TestSignatures sigs;