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

src/richtext/richtextbuffer.cpp

@@ -8317,6 +8317,7 @@ wxString wxRichTextBuffer::GetExtWildcard(bool combine, bool save, wxArrayInt* t
     return wildcard;
 }
 
+#if wxUSE_FFILE && wxUSE_STREAMS
 /// Load a file
 bool wxRichTextBuffer::LoadFile(const wxString& filename, wxRichTextFileType type)
 {
@@ -8345,7 +8346,9 @@ bool wxRichTextBuffer::SaveFile(const wxString& filename, wxRichTextFileType typ
     else
         return false;
 }
+#endif // wxUSE_FFILE && wxUSE_STREAMS
 
+#if wxUSE_STREAMS
 /// Load from a stream
 bool wxRichTextBuffer::LoadFile(wxInputStream& stream, wxRichTextFileType type)
 {
@@ -8374,6 +8377,7 @@ bool wxRichTextBuffer::SaveFile(wxOutputStream& stream, wxRichTextFileType type)
     else
         return false;
 }
+#endif // wxUSE_STREAMS
 
 /// Copy the range to the clipboard
 bool wxRichTextBuffer::CopyToClipboard(const wxRichTextRange& range)