Add anti-skip buffer time when calculating watermark. This fixes the "Anti-Skip Buffe...

Add anti-skip buffer time when calculating watermark. This fixes the "Anti-Skip Buffer" setting. Since the minimum and default value is 5 seconds, this is relevant even when that setting isn't changed. It prevents playback pauses on the 5G iPod, and it should also prevent pauses on other SWCODEC hard drive based players, including FS#10115.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@20747 a1c6a512-1295-4272-9138-f99709370657