[Isolates] Convert more static data either to read-only or to per-isolate.

src/token.h

Index: src/token.h
diff --git a/src/token.h b/src/token.h
index ebc7fea1cd5170fa1cd4d870c09c66c089a43dfd..01be9751f0bf4a0eab997a85681970829d87ec14 100644
--- a/src/token.h
+++ b/src/token.h
@@ -268,9 +268,9 @@ class Token {
   }
 
  private:
-  static const char* name_[NUM_TOKENS];
-  static const char* string_[NUM_TOKENS];
-  static int8_t precedence_[NUM_TOKENS];
+  static const char* const name_[NUM_TOKENS];
+  static const char* const string_[NUM_TOKENS];
+  static const int8_t precedence_[NUM_TOKENS];
   static const char token_type[NUM_TOKENS];
 };