PR libgcj/21692
        * sysdep/descriptor-n.h: New file.
        * sysdep/descriptor-y.h: New file.
        * sysdep/powerpc/descriptor.h: New file.
        * configure.host: Set $descriptor_h appropriate for the host.
        * configure.ac: Link it.
        * configure: Regenerate.
        * stacktrace.cc: Include sysdep/descriptor.h.
        (_Jv_StackTrace::UpdateNCodeMap): Use UNWRAP_FUNCTION_DESCRIPTOR.

From-SVN: r100173