iPhone 5S has the same density as 5 and 4

The iPhone 5S (hw.machine values of iPhone6,1 and iPhone6,2) has the
same pixel density as the iPhone 5.

This fixes crashes on iPhone 5S.

See also:
https://github.com/SVGKit/SVGKit/pull/111
https://github.com/SVGKit/SVGKit/issues/106