vimode: implement hlsearch
This adds vim hlsearch functionality to vimode. All matching patterns found inside the view visible range will be highlighted when a search is initiated from vimode. The feature is turned on by default like in vim.
The following commands have been added: -) set-hlsearch, set-hls to turn it on (vim :set hls[earch]) -) set-nohlsearch, set-nohls to turn it off (vim :set nohls[earch]) -) nohlseach, noh to hide current highlights (vim :noh[lsearch])
BUG: 449641 449643