Implement interactive last-pattern
Implement interactive last-pattern

- if the pattern in the command-line is empty and type
  <Over>(incsearch-next) or <Over>(incsearch-prev), :h last-pattern (@/)
  automatically inserted!
- You can `/<CR>` by default to use last-pattern, but it enables
  incremental cursor moving.
- Of course, it works with /offset too
- ref: #14 Thanks for the idea, @gelguy

haya14busa/incsearch.vim,mydearxym/incsearch.vim