vim-patch:8.1.1614: 'numberwidth' can only go up to 10

Problem:    'numberwidth' can only go up to 10.
Solution:   Allow up to 20. (Charlie Stanton, closes vim/vim#4584)
vim/vim@f8a0712

runtime/doc/options.txt

@@ -4202,7 +4202,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	rows in the window, depending on whether 'number' or 'relativenumber'
 	is set. Thus with the Vim default of 4 there is room for a line number
 	up to 999. When the buffer has 1000 lines five columns will be used.
-	The minimum value is 1, the maximum value is 10.
+	The minimum value is 1, the maximum value is 20.
 
 						*'omnifunc'* *'ofu'*
 'omnifunc' 'ofu'	string	(default: empty)

src/nvim/option.c

@@ -4274,7 +4274,7 @@ static char *set_num_option(int opt_idx, char_u *varp, long value,
   } else if (pp == &curwin->w_p_nuw || pp == &curwin->w_allbuf_opt.wo_nuw) {
     if (value < 1) {
       errmsg = e_positive;
-    } else if (value > 10) {
+    } else if (value > 20) {
       errmsg = e_invarg;
     }
   } else if (pp == &curbuf->b_p_iminsert || pp == &p_iminsert) {

src/nvim/screen.c

@@ -2085,7 +2085,7 @@ win_line (
   int lcs_eol_one = wp->w_p_lcs_chars.eol;     // 'eol'  until it's been used
   int lcs_prec_todo = wp->w_p_lcs_chars.prec;  // 'prec' until it's been used
 
-  /* saved "extra" items for when draw_state becomes WL_LINE (again) */
+  // saved "extra" items for when draw_state becomes WL_LINE (again)
   int saved_n_extra = 0;
   char_u      *saved_p_extra = NULL;
   int saved_c_extra = 0;

src/nvim/testdir/test_options.vim

@@ -231,7 +231,7 @@ func Test_set_errors()
   call assert_fails('set backupcopy=', 'E474:')
   call assert_fails('set regexpengine=3', 'E474:')
   call assert_fails('set history=10001', 'E474:')
-  call assert_fails('set numberwidth=11', 'E474:')
+  call assert_fails('set numberwidth=21', 'E474:')
   call assert_fails('set colorcolumn=-a')
   call assert_fails('set colorcolumn=a')
   call assert_fails('set colorcolumn=1,')

test/functional/options/num_options_spec.lua

@@ -74,7 +74,7 @@ describe(':set validation', function()
     should_fail('foldlevel', -5, 'E487')
     should_fail('foldcolumn', 13, 'E474')
     should_fail('conceallevel', 4, 'E474')
-    should_fail('numberwidth', 11, 'E474')
+    should_fail('numberwidth', 21, 'E474')
     should_fail('numberwidth', 0, 'E487')
 
     -- If smaller than 1 this one is set to 'lines'-1