[IA64] unwind did not work for processes born with CLONE_STOPPED
Minor problem for mainstream. Big problem for CPT, because all the
stopped/traced processes are born in this state, hence they cannot
be checkpointed again due to failing unwind.
The problem was identified as assumption in kernel unwind library
that top level frame is different of syscall frame. It is the case
unless process was born with CLONE_STOPPED.