backtrace size()

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[error] fix in backtrace copy ctor

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[error] backtrace improvements

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[mt] tests

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[tut] tut is external dependency now

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[tests] run unit tests while building rpms

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>