vi: do not distinguish newer vim versions

vi: do not distinguish newer vim versions

Assume vim7 distinction is no longer significant; it was released in 2006
and commonly installed by now.  One is more likely to encounter vim-tiny or
some clone, in which case only vi features are safe.

Also ignore vim8 as it only assigns about 4 keys, all outside of normal
mode.  Rather reclassify all vim extensions as "new" instead of "ext",
freeing the latter for optional features more in line with other pages.