FakeVim: Emulate search more precisely

Submitting search highlights (if 'hlsearch' enabled) in visible editors.

Update highlights after 'nohlsearch' command, 'set hlsearch' and
changing document.

Change-Id: I66ed8c6e9c6e99f3c64f91cdec5ac5feb636d2cb
Reviewed-by: hjk <hjk121@nokiamail.com>