Remove GetStandardCmdLineOptions() from wxGTK

Unfortunately there is no reasonable way to implement this function for all
glibc versions as the information we need is stored in the private
_GOptionGroup struct whose layout has already changed once (in 2.44) and could
change again, so we can't rely on it.

We really need a g_option_group_get_entries() in glib itself, but the request
to add it at http://bugzilla.gnome.org/show_bug.cgi?id=431021 hasn't been
touched since 10 years, so it seems unlikely to happen.

See 99367a1530 (commitcomment-25789514)

include/wx/unix/apptrait.h

@@ -64,8 +64,6 @@ public:
 
 #ifdef __WXGTK20__
     virtual wxString GetDesktopEnvironment() const wxOVERRIDE;
-    virtual wxString GetStandardCmdLineOptions(wxArrayString& names,
-                                               wxArrayString& desc) const wxOVERRIDE;
 #endif // __WXGTK20____
 
 #if defined(__WXGTK20__)