Fix PCH-less build after changes r64139.

As wx/log.h is not included from wx/dynlib.h (via wx/msw/private.h) any
longer, include it from here explicitly.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64202 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/volume.cpp

@@ -32,6 +32,7 @@
         #include "wx/icon.h"
     #endif
     #include "wx/intl.h"
+    #include "wx/log.h"
     #include "wx/hashmap.h"
     #include "wx/filefn.h"
 #endif // WX_PRECOMP