patch 8.1.1106: no test for 'writedelay'

Problem:    No test for 'writedelay'.
Solution:   Add a test.

src/testdir/test_options.vim

@@ -518,3 +518,23 @@ func Test_local_scrolloff()
   set so&
   set siso&
 endfunc
+
+func Test_writedelay()
+  if !has('reltime')
+    return
+  endif
+  new
+  call setline(1, 'empty')
+  redraw
+  set writedelay=10
+  let start = reltime()
+  call setline(1, repeat('x', 70))
+  redraw
+  let elapsed = reltimefloat(reltime(start))
+  set writedelay=0
+  " With 'writedelay' set should take at least 30 * 10 msec
+  call assert_inrange(30 * 0.01, 999.0, elapsed)
+
+  bwipe!
+  delfunc ChangeText
+endfunc

src/version.c

@@ -771,6 +771,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1106,
 /**/
     1105,
 /**/