Padding is miscomputed when writing tags with extended headers

[Bart Massey]

From: Roman Cheplyaka <email address hidden>

There is a bug present in at least the latest version of the package:
when padding is calculated, the size of the extended header is not taken
into account. The calculated padding may exceed the actual padding. This
may cause writeTag to overwrite the first audio frame.

This is especially bad for VBR mp3 files, where the first audio frame
contains the Xing header. If this frame is corrupted, players may
miscalculate the total duration and play only a small part of the file.

The patch is attached.

[Bart Massey (bart-massey)]

Patch validated and applied. Thanks much, Roman!