Let PROMOTED and DEMOTED macros use argument

Let PROMOTED and DEMOTED macros use argument

These macros were expanding to offsets added to what followed them.
Now the thing that followed them is passed to them as an argument.
This will allow them to expand the prmomotion or demotion to a table
lookup, rather than just an addition. Where PROMOTED appeared in a case
label, though, it was just a readability enhancement for the fixed
assignment, and a new macro PROMO equal to the old PROMOTED is introduced
for that.