[Rd] format.default loses matrix structure (PR#8695)

[jhallman at frb.gov]

Full_Name: Jeff Hallman
Version: 2.2.0
OS: Linux
Submission from: (NULL) (132.200.32.34)


format.default() loses matrix structure if big.mark is given

> format(matrix(1:16, 4))
     [,1] [,2] [,3] [,4]
[1,] " 1" " 5" " 9" "13"
[2,] " 2" " 6" "10" "14"
[3,] " 3" " 7" "11" "15"
[4,] " 4" " 8" "12" "16"
> format(matrix(1:16, 4), big.mark = ",")
 [1] " 1" " 2" " 3" " 4" " 5" " 6" " 7" " 8" " 9" "10" "11" "12" "13" "14" "15"
[16] "16"