Fix FS#13009.

This file revealed several problems with our ASF parser:

1)  The packet count in the ASF was actually a 64 bit value,
leading to overflow in very long files.

2)  Seeking blindly trusted the bitrate listed in the ASF header
rather than computing it from the packet size and number of packets.

Fix these problems and fix a few minor issues.

Change-Id: Ie0f68734e6423e837757528ddb155f3bdcc979f3
Fix warning in WMA Pro and remove a c++ comment.

Change-Id: Id9b50c1fdeca4d87f158da717de8958330f027ef