[ruby/reline] Implement vi_prev_char and vi_to_prev_char
https://github.com/ruby/reline/commit/0ad3ee63fa
[ruby/reline] Implement vi_prev_char and vi_to_prev_char
https://github.com/ruby/reline/commit/0ad3ee63fa