This change also makes tor_ersatz_socketpair() follow the same
interface as socketpair() rather than tor_socketpair(), so it now
needs to be wrapped in the same code as socketpair() does.
Fun fact: these files used to be called log.[ch] until we ran into
conflicts with systems having a log.h file. But now that we always
include "lib/log/log.h", we should be fine.