Include wx/checklst.h according to precompiled headers of wx/wx.h (with other minor cleaning).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@39463 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/valgen.cpp

@@ -34,6 +34,7 @@
     #include "wx/button.h"
     #include "wx/listbox.h"
     #include "wx/slider.h"
+    #include "wx/checklst.h"
 #endif
 
 #include "wx/spinctrl.h"
@@ -41,9 +42,6 @@
 #if wxUSE_SPINBTN
     #include "wx/spinbutt.h"
 #endif
-#if wxUSE_CHECKLISTBOX
-    #include "wx/checklst.h"
-#endif
 #if wxUSE_TOGGLEBTN
     #include "wx/tglbtn.h"
 #endif