Commit Briefs
keep the current song if load input was generated by show -p
`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.
add a monitor functionality
this pings all the "interesting" events to clients that issued a IMSG_CTL_MONITOR, except to the one that generated such event.
use fd instead of pid for tx locking
c->iev.ibuf.pid is our pid, not sure why, but fd is just as well as easier to use.