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

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@38868 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/x11/app.cpp

@@ -12,6 +12,10 @@
 // for compilers that support precompilation, includes "wx.h".
 #include "wx/wxprec.h"
 
+#ifndef WX_PRECOMP
+    #include "wx/hash.h"
+#endif
+
 #include "wx/frame.h"
 #include "wx/app.h"
 #include "wx/utils.h"
@@ -26,7 +30,6 @@
 #include "wx/evtloop.h"
 #include "wx/timer.h"
 #include "wx/filename.h"
-#include "wx/hash.h"
 
 #include "wx/univ/theme.h"
 #include "wx/univ/renderer.h"