* mark constant symbols used in preprocessor expressions as used, resolves #40108

compiler/scanner.pas

@@ -2134,11 +2134,13 @@ type
                                   begin
                                     result.free;
                                     result:=texprvalue.create_const(tconstsym(srsym));
+                                    tconstsym(srsym).IncRefCount;
                                   end;
                                 enumsym:
                                   begin
                                     result.free;
                                     result:=texprvalue.create_int(tenumsym(srsym).value);
+//                                    tconstsym(srsym).IncRefCount;
                                   end;
                                 else
                                   ;

tests/webtbs/tw40108.pp

@@ -0,0 +1,14 @@
+{ %opt=-Seh }
+{ %norun }
+program test;
+
+const
+  TheVersion = 1;
+
+begin
+  {$if TheVersion >= 1}
+  writeln('Version 1 or higher');
+  {$else}
+  writeln('Version < 1');
+  {$endif}
+end.