Hi,

I was developing a dynamic module when I noticed that when
'--module-assertions' are enabled I got strange complaints regarding
value to be freed. Namely, Emacs was producing an error message like the
following one:

    Emacs module assertion: Global value was not found in list of 10 globals

I tracked it down to a bug in module_free_global_ref. It's traversal of
the linked list of all allocated global values was flawed and only
considered the head of the list. Please find attached my attempt at
fixing it and a test in Emacs test suite that reproduces the issue.

Regards,
Sergey