The commit mariuszs/nanorc@e5cc8be863
introduced a number of rc files that cause tabs to always show as red
(even with trailing spaces). Adjust the behavior according to changes in
https://github.com/nanorc/nanorc/blob/master/mixins/lint.nanorc, which
seems to be an updated source of the original commit. Make tabs appear
green without trailing characters, red with trailing spaces, and
uncolored when followed by any other character.
