Properly reset rt_next when firing timers.
Let rd_thread_create() assign the thread variable to avoid race conditions.
rd_hex2bin: ignore \n and \r in hex strings
Added rdalert: for alerting the application of various adverse events in librd.
Added rd_opt_description_set(): allows giving extra information along with program usage.
rdlog.h should include syslog.h
Added roll_callback for rd_avg. Will be called when an average period rolls over.