[Google 4.6 Fission] Skeleton debug info sections don't have siblings

[Sterling Augustine]

Hello,

This patch for google 4.6 stops gcc from emitting end-of-sibling
markers for skeleton debug info sections, which don't have siblings.

This fixes an errors reported by readelf. OK for google 4.6?

Sterling


2012-04-20   Sterling Augustine  <saugust...@google.com>

        * gcc/dwarf2out.c (output_skeleton_debug_sections): Fix off-by-one
        error.