Need up-to-datre instructions for configuring for debug build

[Eric S. Raymond]

./waf configure --enable-debug-gdb fails.  gdb complains of not being
able to see dany debugging symbols.

This matters because I may have tripped over a sporadic crash in the
async-DNS-lookup code.  I've seen one trace but I can't be sure of
the location because no debug symbols.

IIRC Hal determined that we have such a bug, inherited from Classic.
I don't know that it ever got fixed.
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>