[Rd] Bug when specifying size of png/jpg/bmp/tiff in mm (PR#13790)

[maurice.berk01 at imperial.ac.uk]

Full_Name: Maurice Berk
Version: 2.8.1
OS: RedHat Linux 64bit
Submission from: (NULL) (155.198.195.25)


The offending line in all 4 functions is:

width <- switch(units, `in` = res, cm = res/2.54, mm = 1/25.4,
        px = 1) * width

The case for mm is clearly incorrect