tabline: add consistent tab label to the end

closes #1882
closes #1883

autoload/airline/extensions/tabline.vim

@@ -229,3 +229,9 @@ function! airline#extensions#tabline#add_label(dict, type)
           \ get(g:, 'airline#extensions#tabline#'.a:type.'_label', a:type))
   endif
 endfunction
+
+function! airline#extensions#tabline#add_tab_label(dict)
+  if tabpagenr('$') > 1
+    call a:dict.add_section_spaced('airline_tabmod', printf('%s %d/%d', "tab", tabpagenr(), tabpagenr('$')))
+  endif
+endfunction

autoload/airline/extensions/tabline/buffers.vim

@@ -140,9 +140,7 @@ function! airline#extensions#tabline#buffers#get()
     call airline#extensions#tabline#add_label(b, 'buffers')
   endif
 
-  if tabpagenr('$') > 1
+  call airline#extensions#tabline#add_tab_label(b)
-    call b.add_section_spaced('airline_tabmod', printf('%s %d/%d', "tab", tabpagenr(), tabpagenr('$')))
-  endif
 
   let s:current_bufnr = cur
   let s:column_width = &columns

autoload/airline/extensions/tabline/tabs.vim

@@ -92,6 +92,7 @@ function! airline#extensions#tabline#tabs#get()
       call airline#extensions#tabline#add_label(b, 'buffers')
     endif
   endif
+  call airline#extensions#tabline#add_tab_label(b)
 
   let s:current_bufnr = curbuf
   let s:current_tabnr = curtab