patch 8.1.1168: not all screen update code of terminal is executed in tests

Problem:    Not all screen update code of the terminal window is executed in
            tests.
Solution:   Redraw before taking a screenshot.

src/testdir/screendump.vim

@@ -113,6 +113,10 @@ func VerifyScreenDump(buf, filename, options, ...)
   let reference = 'dumps/' . a:filename . '.dump'
   let testfile = 'failed/' . a:filename . '.dump'
 
+  " Redraw to execut the code that updates the screen.  Otherwise we get the
+  " text and attributes only from the internal buffer.
+  redraw
+
   let did_mkdir = 0
   if !isdirectory('failed')
     let did_mkdir = 1

src/version.c

@@ -771,6 +771,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1168,
 /**/
     1167,
 /**/