Initial implementation of the debuginfo API This patchset adds so_info and durin, which are used in debug info or callsite analysis. The developer is expected to use the SO info API documented in `include/babeltrace/so-info.h`. Durin is only used internally by so_info as a wrapper around `libdw`. The analysis itself is implemented in the new `lib/debuginfo.c`. This introduces a dependency on `libelf` and `libdw` from elfutils. The feature can be disabled at configure time with the `--disable-debuginfo` flag. Signed-off-by: Antoine Busque <abusque@efficios.com> Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>