Compilation fix for wxMSW 64 bit build with icc.

This compiler doesn't want to narrow INVALID_HANDLE_VALUE to int, so use
wxUIntPtr instead.

See #16233.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76659 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775