Issue 3019.5

This should add the property 'maxcpus' to a buildslaves configuration. If 'maxcpus' is not specified it defaults to 'None' which uses 'multiprocessing.cpu_count()' to receive the max amount of CPUs.
This isn't present in Python-2.4, which the buildslave still supports.

Can you add conditionals to the import so that it still runs (just without this property) in that mode?