document (and check for it with assert) that wxGetKeyState(WXK_[LMR]BUTTON) doesn't work (patch 1156279)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@32970 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/unix/utilsx11.cpp

@@ -764,6 +764,9 @@ KeySym wxCharCodeWXToX(int id)
 
 bool wxGetKeyState(wxKeyCode key)
 {
+    wxASSERT_MSG(key != WXK_LBUTTON && key != WXK_RBUTTON && key !=
+        WXK_MBUTTON, wxT("can't use wxGetKeyState() for mouse buttons"));
+
 #if defined(__WXX11__)
     Display *pDisplay = (Display*) wxApp::GetDisplay();
 #elif defined(__WXGTK__)