Problem: 'nowrap' in a modeline may hide malicious code.
Solution: Forcibly use '>' as 'listchars' "extends" if 'nowrap' was set
from a modeline (zeertzjq).
Manual `:setlocal nowrap` disables this behavior. There is a separate
problem with `:set nowrap` that also applies to some other options.
related: vim/vim#18214
related: vim/vim#18399closes: vim/vim#184259d5208a931
Cherry-pick some test_modeline.vim changes from patches 9.0.{0363,0626}.
0fa0717d4e