patch 8.0.1536: quotestar test is flaky when using the GUI

Problem:    Quotestar test is flaky when using the GUI.
Solution:   Add check that the star register arrived at the server.  Increase
            timeouts.

src/testdir/test_quotestar.vim

@@ -65,24 +65,23 @@ func Do_test_quotestar_for_x11()
 
   " Takes a short while for the server to be active.
   call WaitFor('serverlist() =~ "' . name . '"')
-  call assert_match(name, serverlist())
 
   " Wait for the server to be up and answering requests.  One second is not
   " always sufficient.
   call WaitFor('remote_expr("' . name . '", "v:version", "", 2) != ""')
 
-  " Clear the *-register of this vim instance.
-  let @* = ''
-
-  " Try to change the *-register of the server.
+  " Clear the *-register of this vim instance and wait for it to be picked up
+  " by the server.
+  let @* = 'no'
   call remote_foreground(name)
+  call WaitFor('remote_expr("' . name . '", "@*", "", 1) == "no"', 3000)
+
+  " Set the * register on the server.
   call remote_send(name, ":let @* = 'yes'\<CR>")
-  call WaitFor('remote_expr("' . name . '", "@*", "", 1) == "yes"')
-  call assert_equal('yes', remote_expr(name, "@*", "", 2))
+  call WaitFor('remote_expr("' . name . '", "@*", "", 1) == "yes"', 3000)
 
   " Check that the *-register of this vim instance is changed as expected.
-  call WaitFor('@* == "yes"')
-  call assert_equal('yes', @*)
+  call WaitFor('@* == "yes"', 3000)
 
   " Handle the large selection over 262040 byte.
   let length = 262044

src/version.c

@@ -778,6 +778,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1536,
 /**/
     1535,
 /**/