Add event_enable_debug_logging() to control use of debug logs Previously, debug logs were turned on if you built with -DUSE_DEBUG and off otherwise. This make builds with -DUSE_DEBUG hideously slow and other builds unable to get debug logs. This is based off a patch by Ralph Castain from October. It tries a little harder to avoid needless function calls, it doesn't require stdbool, and makes the controlling parameter a mask rather than a boolean so that we can later support enabling only the debugging messages for the parts of Libevent you're trying to debug.