[interpreter] Add basic framework for bytecode handler code generation.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index c84b8b9f9286f64604ab97b4cc4e01e2625738ff..585c5b8bf2f5f54bb3013bdcdff0538c12318c64 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -88,6 +88,9 @@ class PromiseOnStack;
 class Redirection;
 class Simulator;
 
+namespace interpreter {
+class Interpreter;
+}
 
 // Static indirection table for handles to constants.  If a frame
 // element represents a constant, the data contains an index into
@@ -1326,6 +1329,8 @@ class Isolate {
   HeapProfiler* heap_profiler_;
   FunctionEntryHook function_entry_hook_;
 
+  interpreter::Interpreter* interpreter_;
+
   typedef std::pair<InterruptCallback, void*> InterruptEntry;
   std::queue<InterruptEntry> api_interrupts_queue_;