1. wxLoad/SaveFileSelector return "wxString" instead of "char *"

1. wxLoad/SaveFileSelector return "wxString" instead of "char *"
2. WXDLLEXPORT was misplaced in a couple of places (hopefully my chanegs won't
   break compilation for other compilers)
3. Some VC++ warnings suppressed in socket code

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@1464 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775