This should keep things nicely extensible, since additional data can be
done in the data space and found using defs. This gets the compilation
units into the sym file.
The compilation unit stores the directory from which qfcc was run and
any source files mentioned. This is similar to dwarf's compilation unit.
Right now, this is the only data in the new debug space, but more might
come in the future so it seems best to treat the debug space separately
in the object files.
I decided that stopping in between function calls that are on the same
line is a good thing as it gives a chance to skip over the first but
step into the second.
