Disable the dump_desc() function.
It can be called with strings that should have been length-delimited, but which in fact are not. This can cause a CPU-DoS bug or, in a worse case, a crash. Since this function isn't essential, the best solution for older Tors is to just turn it off. Fixes bug 40286; bugfix on 0.2.2.1-alpha when dump_desc() was introduced.