Some Unicode compilation fixes. This Unicode stuff in file functions is

Some Unicode compilation fixes. This Unicode stuff in file functions is
always so hard to get right, it seems... I don't like that wxStat isn't
a Unicode wrapper for the real Linux libc stat(), so the caller needs to
convert it for wxStat, but not for e.g. wxRename... this is inconsistent,
so it's not surprising people don't get it right, I guess.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@9608 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775