Fix wxMSW build without PCH after recent wxPanel changes.

Add missing include of wx/bitmap.h in !WX_PRECOMP case.

Closes #13060.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67269 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/panel.cpp

@@ -24,6 +24,7 @@
 #endif
 
 #ifndef WX_PRECOMP
+    #include "wx/bitmap.h"
     #include "wx/brush.h"
     #include "wx/panel.h"
 #endif // WX_PRECOMP