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

match the struct sio_par

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

it's easier / simpler for scripts to do $ amused monitor next,prev,jump rather than $ amused monitor | egrep --line-buffered 'next|prev|jump'

this will allow to remove the `got_stop' hack in player.c

`amused show -p' generates a listing in the form of song > current song song ... This adds an heuristic to `amused load' so that the current song can be set if it's prefixed by "> ". It's particularly useful when re-importing the state from a previous run.

this pings all the "interesting" events to clients that issued a IMSG_CTL_MONITOR, except to the one that generated such event.