This causes libdw to not be able to be linked with a C++ program.
Has been resolved upstream, and temporary measures have been comitted to the
2006-05-29 Adam Jocksch <email@example.com>
* Makefile.am: Added libdwfl.a.
* elfutils/libdw/libdw.h: Added extern "C" as a temporary fix.
* elfutils/libdwfl/libdwfl.h: Ditto.