no static functions or data in xref

[David DeHaven]

cflow version 1.6

File play.c (and probably others) from gnu backgammon: 
gnubg-release-1.06.002-sources.tar.gz

Tried various combinations of these commands:

        cflow -i x -x -o xxxx.xrf play.c

        grep DiceRolled xxxx.xrf

Running on Debian 10

Architecture x86-64

Linux Kernel 4.19.0

Also stripped out static keyword using sed from the file as a test and 
then it works OK. This is the only way I have been able to make it work 
(but of course there are no statics to fail with) and that is the way i 
am running at this time.