bug#19554: 25.0.50; void-function xref-marker-stack-empty-p and subsequent abort

[martin rudalics]

> Doesn't happen to me here with the current master.

I understand that meanwhile.

> Could it be that you have stale *.elc files that need to be
> recompiled?

Might be, but where?  I spent an hour boostrapping yesterday after make
distclean and the oldest .elc file in my entire trunk is cconv.elc.

I also don't have the slightest idea where `xref-marker-stack-empty-p'
could get called from.

martin