Fix build with wxUSE_FFILE=0.

Add the missing "#if wxUSE_FFILE" checks and add fallbacks to wxFile if it's
available.

Closes #15353.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74596 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/richtext/richtextprint.h

@@ -165,11 +165,15 @@ public:
     virtual ~wxRichTextPrinting();
 
     /// Preview the file or buffer
+#if wxUSE_FFILE && wxUSE_STREAMS
     bool PreviewFile(const wxString& richTextFile);
+#endif
     bool PreviewBuffer(const wxRichTextBuffer& buffer);
 
     /// Print the file or buffer
+#if wxUSE_FFILE && wxUSE_STREAMS
     bool PrintFile(const wxString& richTextFile, bool showPrintDialog = true);
+#endif
     bool PrintBuffer(const wxRichTextBuffer& buffer, bool showPrintDialog = true);
 
     /// Shows page setup dialog