Remove old compatibility tools from asciitable that are not needed in astropy

The old asciitable worked for python < 2.4 and worked without numpy.
Some of the compatibility stuff for that was still in the io.ascii
codebase, although this situation can never arise in astropy (it requires
numpy anyway).
Origninally, it was left there to make it easier to develop io.ascii and
asciitable in parallel, but by now io.ascii is so closely related to
astropy.table that it is unfeasable anyway to remake a stand-alone package
based on this. Thus, I removed the old code.