Replace use of "global" variables with "module level" variables

Brad expressed modest dismay that the Spec contains the phrase "Global" variables
rather than "Module level" variables.  I have performed a global replace, no pun intended,
to address this.

This may be a poor time to make this change in which case I will cheerfully delete this branch
and revisit in the next cycle.

This sounds a bit awkward.  I suggest "at the module level".