1. a couple of compilation warnings fixed (strconv/listctrl)

1. a couple of compilation warnings fixed (strconv/listctrl)
2. now reenable windows disabled by wxWindowDisabler slightly earlier:
   this solves the problem with "wrong" window being brought to top and
   eliminates the need for BringWindowToTop() and SetActiveWindow() in
   our code
3. style wxFRAME_FLOAT_ON_PARENT is now obsolete and unused, all frames
   have WS_EX_APPWINDOW style and appear on the taskbar

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@8487 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775