bootstrap error due to constexpr in go/gofrontend/ast-dump.cc

[Martin Sebor]

A recent change (r269633 AFAICS) introduced the constexpr keyword
into go which breaks bootstrap with a C++ 98 compiler.  I fixed
it like this in my tree but haven't fully tested it.  I just
thought I'd send a heads up before others run into it.

Martin

===================================================================
--- go/gofrontend/ast-dump.cc   (revision 269652)
+++ go/gofrontend/ast-dump.cc   (working copy)
@@ -610,7 +610,7 @@ class Type_dumper
                      const char *tag);
   std::pair<bool, unsigned> lookup(const Type*);

-  static constexpr unsigned notag = 0xffffffff;
+  static const unsigned notag = 0xffffffff;

  private:
   const Type* top_;