Fix to Wenum-compare

It seems the purpose is to define a constant as an anonymous enum.
that behaviour triggers the enum  compare. Let's make it a constant.

cde/programs/nsgmls/Mode.h

@@ -83,7 +83,7 @@ enum Mode {
 
 const int nModes = mconnetMode + 1;
 
-enum { minShortrefMode = econMode };
+const int minShortrefMode = econMode;
 
 #ifdef SP_NAMESPACE
 }