libunwind: make adding wrong backing segment non-fatal

Signed-off-by: Martin Milata <mmilata@redhat.com>
Signed-off-by: Jakub Filak <jfilak@redhat.com>
unwind: factor out libelf initialization

Signed-off-by: Martin Milata <mmilata@redhat.com>
Signed-off-by: Jakub Filak <jfilak@redhat.com>
unwind: factor out build_id+offset resolution

Signed-off-by: Martin Milata <mmilata@redhat.com>
Signed-off-by: Jakub Filak <jfilak@redhat.com>
unwind: move get_signal_number to common code

The function body was not changed.

Signed-off-by: Martin Milata <mmilata@redhat.com>
Signed-off-by: Jakub Filak <jfilak@redhat.com>
Add function for creating core stacktrace from gdb

Needed as on some distributions there is neither libunwind nor elfutils
with unwinder.

Signed-off-by: Martin Milata <mmilata@redhat.com>
Signed-off-by: Jakub Filak <jfilak@redhat.com>
Add sr_abrt_create_core_stacktrace_from_gdb

High-level function used by ABRT.

Signed-off-by: Martin Milata <mmilata@redhat.com>
Signed-off-by: Jakub Filak <jfilak@redhat.com>