fix for issue #1447 (#1462)

Added case for OpCode_BaseFontName. This opcode in spec but practically unused.
Added a comment for default case which can't be hit

src/hb-ot-cff1-table.hh

@@ -656,7 +656,7 @@ struct NameDictValues
   static inline enum NameDictValIndex name_op_to_index (OpCode op)
   {
     switch (op) {
-      default:
+      default: // can't happen - just make some compiler happy
       case OpCode_version:
 	return version;
       case OpCode_Notice:
@@ -673,6 +673,8 @@ struct NameDictValues
 	return postscript;
       case OpCode_FontName:
 	return fontName;
+      case OpCode_BaseFontName:
+	return baseFontName;
     }
   }