vim:au: Improve clearing of old selection highlight

Because of the deferring of the highlight, the old selection highlight
was deleted only when a new one was created. Introduce a second timer
that makes sure that the old highlight is cleared earlier.

.config/vim/vimrc.d/80-autocommands.vim

@@ -110,6 +110,10 @@ function! s:highlight_selection()
 	" Kill the possibly already running timer
 	if exists('w:selection_timer_id')
 		call timer_stop(w:selection_timer_id)
+		" Make sure that the old selection is deleted soon-ish
+		if exists("w:visual_match_ids") && !exists("w:selection_clear_timer_id")
+			let w:selection_clear_timer_id = timer_start(150, 's:clear_visual_timer')
+		endif
 	endif
 
 	" Delay the highlight by 100ms so that not every selection is highlighted
@@ -121,6 +125,11 @@ endfunction
 function! s:_highlight_selection(timer)
 	unlet w:selection_timer_id
 
+	if exists("w:selection_clear_timer_id")
+		call timer_stop(w:selection_clear_timer_id)
+		unlet w:selection_clear_timer_id
+	endif
+
 	let l:old_reg = getreg('"')
 	let l:old_regtype = getregtype('"')
 	" NOTE: The yank needs to be silent to mute the 'n lines yanked'
@@ -189,6 +198,11 @@ function! s:clear_highlights(what = s:CLEAR_HIGHS_ALL)
 	endif
 endfunction
 
+function! s:clear_visual_timer(timer)
+	unlet w:selection_clear_timer_id
+	call s:clear_highlights(s:CLEAR_HIGHS_VISUAL)
+endfunction
+
 augroup highlight_current
 	au!
 	" TODO: `viw` when on the last character of the word does not trigger