Fix compilation with recent MinGW64 versions.

src/ast.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 105 matching lines @@
   V(BinaryOperation)                            \
   V(CompareOperation)                           \
   V(ThisFunction)
 
 #define AST_NODE_LIST(V)                        \
   DECLARATION_NODE_LIST(V)                      \
   MODULE_NODE_LIST(V)                           \
   STATEMENT_NODE_LIST(V)                        \
   EXPRESSION_NODE_LIST(V)
 
-#ifdef WIN32
-#undef Yield
-#endif
-
 // Forward declarations
 class AstConstructionVisitor;
 template<class> class AstNodeFactory;
 class AstVisitor;
 class Declaration;
 class Module;
 class BreakableStatement;
 class Expression;
 class IterationStatement;
 class MaterializedLiteral;
@@ skipping 3103 matching lines @@
  private:
   Isolate* isolate_;
   Zone* zone_;
   Visitor visitor_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_