Rockbox

Repost as the attachment was missed/lost.

get_vorbis_metadata may return a too small sample count
(depending on the ogg file beeing analysed).
The reasons are:
- the last five bytes of a data chunk in buffer are
always discarded if no "OggS" mark was found in buffer
so far. Hence the beginning of a header in these five
bytes is lost sight of.
- Moving an OggS mark to start of buffer (after it was
found in the last 17 bytes of a data chunk) doesn't
work like expected (out of boundary read, buffer
garbling).
- If a header was found in buffer it is not checked if
there are other ones. OK, as the buffer is very small
this is unlikely to happen.

A patch is hopefully attached this time.