2013/8/16 Darrell Anderson <darrella@hushmail.com>

>> Here is propoused patch which checks if demangle.h is present.
>>
>Darrell, I have demangle.h on my system, so it's up to you to test
>it.

Actually anybody can test --- just temporarily rename or move
/usr/include/demangle.h. :-)

The previous patch makes turning on the debug quite tricky, so better to remove the ifdef's with NDEBUG in backtrace_symbols.c.

I've tested the build both with and without demangle.h and seems everything is ok. so retest