This symbol was undefined which meant that it defaulted to being equal
to zero. Since this was the value tested for in all cases, then all
cases of this macro test were enabled which was not very clear.
Looking at the code, it appears this is intended to guard a debugging
mode enabling slower, but more readable rendering code and other graphics
information. This should probably be migrated to a boolean flag of the
engine (since debug already exists) or a ScummVM debug level / flag.
This changes also removes a large number of GCC warnings regarding
use of undefined macro symbols.
