Just because the user requested the seek index to be ignored, we can't
just skip essential headers. At least tags are often located at the end
of the file, and the old code simply ignored the seekhead for all
elements, not just the cue index. Also, it looks like it used the index
even if IGNIDX was set if the cue index was located in the beginning of
the file.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>