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

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@39247 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/gdicmn.cpp

@@ -30,13 +30,13 @@
     #include "wx/dc.h"
     #include "wx/pen.h"
     #include "wx/brush.h"
+    #include "wx/palette.h"
 #endif
 
 #include "wx/bitmap.h"
 #include "wx/icon.h"
 #include "wx/cursor.h"
 #include "wx/font.h"
-#include "wx/palette.h"
 #include "wx/settings.h"
 #include "wx/hashmap.h"