C++ operator overload over enum tag types

regression/cpp/enum5/main.cpp

@@ -1,4 +1,4 @@
-#include <cassert>
+#include <assert.h>
 
 enum IMPH_STATE
 {

regression/cpp/enum5/test.desc

@@ -1,4 +1,4 @@
-KNOWNBUG
+CORE
 main.cpp
 
 ^EXIT=0$

src/cpp/cpp_typecheck_expr.cpp

@@ -433,7 +433,7 @@ bool cpp_typecheckt::overloadable(const exprt &expr)
 
     if(t.id()==ID_struct ||
        t.id()==ID_union ||
-       t.id()==ID_c_enum)
+       t.id()==ID_c_enum || t.id() == ID_c_enum_tag)
       return true;
   }