This adds the internal management of the seeking, as well as the decoder backends bits.

meh, just to please the compiler. Global variables are guaranteed to be zeroed so not specifying a value shouldn't matter, yet it complains.

match the struct sio_par

if the server fails to start for wathever reason, we end up looping in ctl_connect indefinitely as we try to spawn the deamon (that dies) and try to connect to it. Add an arbitrary maximum number of retries before giving up. Reported by sikmir in the GitHub issue #1, thanks!

makes the player process optionally send back a string describing the failure to provide a better and more coincise error message. This turns the syslog message(s): amused: unknown file type amused: failed to play, skipping /home/op/pics/phos.jpg into: amused: unknown file type; skipping /home/op/pics/phos.jpg