Add mapping to toggle autoclose option

The current tagbar_autoclose state will be displayed in the statusline.
Also change the "hide nonpublic" flag to "v" to match the mapping and
properly document the statusline flags.

autoload/tagbar.vim

@@ -938,10 +938,11 @@ function! s:MapKeys() abort
         \ ['openallfolds',  'SetFoldLevel(99, 1)'],
         \ ['closeallfolds', 'SetFoldLevel(0, 1)'],
         \
-        \ ['togglesort', 'ToggleSort()'],
-        \ ['zoomwin',    'ZoomWindow()'],
-        \ ['close',      'CloseWindow()'],
-        \ ['help',       'ToggleHelp()'],
+        \ ['togglesort',      'ToggleSort()'],
+        \ ['toggleautoclose', 'ToggleAutoclose()'],
+        \ ['zoomwin',         'ZoomWindow()'],
+        \ ['close',           'CloseWindow()'],
+        \ ['help',            'ToggleHelp()'],
     \ ]
 
     for [map, func] in maps
@@ -1808,12 +1809,12 @@ function! s:InitWindow(autoclose) abort
     setlocal foldmethod&
     setlocal foldexpr&
 
+    let w:autoclose = a:autoclose
+
     call s:SetStatusLine('current')
 
     let s:new_window = 1
 
-    let w:autoclose = a:autoclose
-
     if has('balloon_eval')
         setlocal balloonexpr=TagbarBalloonExpr()
         set ballooneval
@@ -3666,6 +3667,12 @@ function! s:ToggleHideNonPublicTags() abort
     call s:SetStatusLine('current')
 endfunction
 
+" s:ToggleAutoclose() {{{2
+function! s:ToggleAutoclose() abort
+    let g:tagbar_autoclose = !g:tagbar_autoclose
+    call s:SetStatusLine('current')
+endfunction
+
 " s:IsValidFile() {{{2
 function! s:IsValidFile(fname, ftype) abort
     call s:debug('Checking if file is valid [' . a:fname . ']')
@@ -3727,13 +3734,21 @@ function! s:SetStatusLine(current)
         let fname = ''
     endif
 
+    let flags = []
+    let flags += exists('w:autoclose') && w:autoclose ? ['c'] : []
+    let flags += g:tagbar_autoclose ? ['C'] : []
+    let flags += g:tagbar_hide_nonpublic ? ['v'] : []
+
     if exists('g:tagbar_status_func')
-        let args = [current, sort, fname]
+        let args = [current, sort, fname, flags]
         let &l:statusline = call(g:tagbar_status_func, args)
     else
         let colour = current ? '%#StatusLine#' : '%#StatusLineNC#'
-        let hide = g:tagbar_hide_nonpublic ? '[h] ' : ''
-        let text = colour . '[' . sort . '] ' . hide . fname
+        let flagstr = join(flags, '')
+        if flagstr != ''
+            let flagstr = '[' . flagstr . '] '
+        endif
+        let text = colour . '[' . sort . '] ' . flagstr . fname
         let &l:statusline = text
     endif