#19 Support for backtraces

[Johan Walles]

Here's a patch that adds support for printing
backtraces for all reported syscalls. It does its
thing using libunwind
(http://www.hpl.hp.com/research/linux/libunwind/).
I've tested it on IA64 only. In theory it should work
on any other platform where libunwind exists.

I haven't added any command line flag for enabling /
disabling printing of backtraces. With this patch,
backtraces are always printed.

The configure script checks for libunwind, and if
libunwind isn't found the configure script bails with
an error.

Is this something you'd consider including in the
official strace? If so, what do I need to do before it
can get accepted? I have a few ideas myself, but I'd
like to hear *your* opinion :-).

[Johan Walles]

Diff for libunwind support

[Eugene Syromyatnikov]

Stack unwinding support was added in strace 4.9.