This patch makes the progress bar behavior better when
encoding to formats like flac where the bitrate isn't
Old behavior: Progress bars in both track and overall
displays are always full when encoding. Track display
says "Inf x" and overall says "100%".
New behavior: Track progress bar is half full while
encoding, and the
speed is shown as "? x". Overall progress bar reflects
completed tracks, where a track currently being
encoding counts as 1/2 of a completed track.
The new behavior is triggered by
ginfo->kbits_per_sec==0, so if the user has entered a
dummy bitrate, it will act as before.
My changes don't produce the ideal behavior of actually
second-by-second progress, but it seems that to get
that would require
much more invasive changes.