Add wxTLW::SetModified to allow apps to set the TLW's dirty state. On Mac this gives us the dot in the close button, not implemented elsewhere yet.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62796 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/toplevel_osx.cpp

@@ -186,3 +186,13 @@ bool wxTopLevelWindowMac::IsActive()
 {
     return m_nowpeer->IsActive();
 }
+
+void wxTopLevelWindowMac::SetModified(bool modified)
+{
+    m_nowpeer->SetModified(modified);
+}
+
+bool wxTopLevelWindowMac::GetModified() const
+{
+    return m_nowpeer->GetModified();
+}