Write traceback file to the same directory as core file

Write traceback file to the same directory as core file

The traceback files could overwrite each other on systems which do not
use different core dump file names for different processes.  Prevent
that by writing the traceback file to the same directory as the core
dump file.

These changes still do not prevent the operating system from overwriting
a core dump file if the same binary crashes multiple times in the same
directory and core dump files are named identically for different
processes.