Added wxConv_gdk (wrapper for gdk_mbstowcs and gdk_wcstombs, which use X calls instead of libc calls), which should probably not be used, but is now there for completeness, and in case it's useful after all. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@2158 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775