Require use of digraphs in macro redefinitions to match the original.

This is part of the general requirement that macro redefinitions be "identical" as defined in the standard.

This affects code like:

#define x [
#define x <:

Scanner.pas

@@ -2650,7 +2650,12 @@ var
                   goto 3;
                if tk1^.token.class = tk2^.token.class then
                   case tk1^.token.class of
-                     reservedWord, reservedSymbol: ;
+                     reservedWord: ;
+                     reservedSymbol:
+                        if tk1^.token.isDigraph <> tk2^.token.isDigraph then
+                           if tk1^.token.kind in [lbrackch,rbrackch,lbracech,
+                              rbracech,poundch,poundpoundop] then
+                              goto 3;
                      identifier:
                         if tk1^.token.name^ <> tk2^.token.name^ then
                            goto 3;