Define wx[U]IntPtr as long, not [s]size_t, in 32 bit builds.

Define wx[U]IntPtr as long, not [s]size_t, in 32 bit builds.

Defining wxIntPtr as ssize_t or long in 32 bit builds doesn't really change
anything but using long means that we can replace longs in the existing API
with wxIntPtr without breaking compatibility, like in wxListCtrl::SortItems().
It is also more compatible with 64 bit builds where wxIntPtr is long already.
So it has some minor advantages and no apparent drawbacks.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67732 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775