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

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@39428 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/checkbox.cpp

@@ -1,5 +1,5 @@
 /////////////////////////////////////////////////////////////////////////////
-// Name:        msw/checkbox.cpp
+// Name:        src/msw/checkbox.cpp
 // Purpose:     wxCheckBox
 // Author:      Julian Smart
 // Modified by:
@@ -26,8 +26,9 @@
 
 #if wxUSE_CHECKBOX
 
+#include "wx/checkbox.h"
+
 #ifndef WX_PRECOMP
-    #include "wx/checkbox.h"
     #include "wx/brush.h"
     #include "wx/dcscreen.h"
     #include "wx/settings.h"
@@ -212,7 +213,7 @@ wxSize wxCheckBox::DoGetBestSize() const
     wxString str = wxGetWindowText(GetHWND());
 
     int wCheckbox, hCheckbox;
-    if ( !str.IsEmpty() )
+    if ( !str.empty() )
     {
         GetTextExtent(wxStripMenuCodes(str), &wCheckbox, &hCheckbox);
         wCheckbox += s_checkSize + GetCharWidth();