Drop c90 compiler support
I think it would be reasonable to add a configure check which complains if all your compiler supports is c90, and add a switch to override that behaviour documenting that if you use it without telling us, Tor will stop working for you with 0.2.7. That way, we don't prevent anyone from building Tor today, we still enfore c90 code for now in 0.2.6 without breaking it accidentally like we certainly would if we just lifted the requirement, and have a smooth way forward. Happy to cook up a patch if people think this is a good idea.