player: minor changes

This shouldn't change anything functionally.

Change the A/V desync message. --framedrop is enabled by default now, so
the text must be changed a little. I've never heard of audio outputs
messing up A/V sync recently, so remove that part.

Remove the unused ao_pts field.

Reorder 2 A/V sync related expressions so that they look the same.
input: stdin is 0, not 1

Oops. I can never remember this right.