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