Bugfix:
small difference in x aligmnent calculation in multibar meant slider occasionally did not align with scale. Fixed.

Improvements:
Do not perform pixmap updates/feedback calculation when a panel is not mapped.

Throw away pixmap updates/exposes if display thread is lagging behind
computation (avoid UI being permanently behind playback and ignoring
user input)


git-svn-id: https://svn.xiph.org/trunk/postfish@5847 0101bb08-14d6-0310-b084-bc0e0c8e3800