Hi. Here are two small patches to improve handling of images loaded with
the imagemagick backend. They are:

1. Accept integer :rotation parameters. Previously only floating-point
ones worked

2. If an EXIF orientation tag exists and no explicit :rotation exists,
use the orientation. This happens early in the processing, so all the
data (width, height, etc) that emacs sees applies to the rotated image.

The motivation for this was that I was tired of seeing upside-down
photos in my mu4e mail.

Thanks!