Simply "backed" and "virutal". Backed spaces have memory allocated to them
while virtual spaces do not. Virtual spaces are intended for local
variables and entity fields.
Since there is now a proper symbol table, defs are now just references to
memory locations and the symbol table takes care of duplicates.
Also, start using far data for ObjQC structures.
The qfo functions have been stubbed out until I figure out what to do with
object files in the new scheme.
