[perl #57630] [DEPRECATED] "DOD" acronym

[Christoph Otto via RT]

I've been working on replacing references to "DOD" with "GC" (uc or lc,
as appropriate).  Usually this is fine, but some code refers to GC and
DOD separately such that renaming wouldn't work (e.g.
include/parrot/resources.h:176).  

When code does this sort of thing, what'd be a good name to use (or is
there even a good general case)?  My first instinct is to do something
like change e.g. "DOD_block_level" to "mark_block_level", but I don't
know if this would generally make sense or if there are cases where it'd
result in unclear or deceptive names.  Would "mark" be a good name to
use here, or would something else be a better fit?