Propagate new ctkBackTracePrivate::trace signature

See d6c078190f8ec8bd68a7320e8b2d8eff5fa4964a
Merge branch 'fix-ctkbacktrace-out-of-line-definition'

* fix-ctkbacktrace-out-of-line-definition:
  Propagate new ctkBackTracePrivate::trace signature