Python Exif Parser

Several programs I used (e.g. IrfanView, Ulead Photo
Explorer) do lossless JPEG transforms, but when they
write the .jpg file back out, they add a JFIF marker
in the front of the file before the EXIF marker.

exif.parse() expects the first marker in a JPEG file
to be an EXIF marker, and therefore does not recognize
these JFIF files as having EXIF.

I have a small patch to exif.parse() to handle these
JFIF-marked files. The diff is attached.

I don't know whether you think this is the best way to
fix this problem, but it worked for me.

Dan Halbert