Reinstate g:solarized_use16.

Neovim ignores `&t_Co` and `&term`, so it is not possible in Neovim to
use the ANSI colors when `termguicolors` is not set.

Re-add this option to override the value of `s:t_Co`.

Fixes https://github.com/lifepillar/vim-solarized8/issues/71.

templates/solarized8.colortemplate

@@ -9,10 +9,7 @@ Include:        _info.colortemplate
 Include: _help.colortemplate
 # }}}
 
-#let s:italics = s:italics && get(g:, '@optionprefix_italics', 1)
-#let s:termtrans = get(g:, '@optionprefix_termtrans', 0) && !has('gui_running')
-
-Include: _linked_groups.colortemplate
+Include: _global.colortemplate
 
 Variant: gui 256 16