waf: a better way to detect duplicated symbols

waf: a better way to detect duplicated symbols

this detects when we have the same symbol linked in twice in any
binary by using ldd and nm on the binary and its associated libraries.

Some of these duplicates are caused by a subsystem being linked twice,
and some are caused by two versions of the same function name being
linked into a binary

Pair-Programmed-With: Andrew Bartlett <abartlet@samba.org>

Autobuild-User: Andrew Tridgell <tridge@samba.org>
Autobuild-Date: Wed Apr  6 06:44:14 CEST 2011 on sn-devel-104