patch 8.0.0633: the client-server test is still a bit flaky

Problem:    The client-server test is still a bit flaky.
Solution:   Wait a bit for the GUI to start.  Check that the version number
            can be obtained.

src/testdir/test_clientserver.vim

@@ -45,7 +45,7 @@ func Test_client_server()
   call assert_equal('yes', remote_expr(name, "testvar", "", 2))
 
   if has('unix') && has('gui') && !has('gui_running')
-    " Running in a terminal and the GUI is avaiable: Tell the server to open
+    " Running in a terminal and the GUI is available: Tell the server to open
     " the GUI and check that the remote command still works.
     " Need to wait for the GUI to start up, otherwise the send hangs in trying
     " to send to the terminal window.
@@ -56,7 +56,9 @@ func Test_client_server()
       call remote_send(name, ":gui -f\<CR>")
     endif
     " Wait for the server to be up and answering requests.
+    sleep 100m
     call WaitFor('remote_expr("' . name . '", "v:version", "", 1) != ""')
+    call assert_true(remote_expr(name, "v:version", "", 1) != "")
 
     call remote_send(name, ":let testvar = 'maybe'\<CR>")
     call WaitFor('remote_expr("' . name . '", "testvar", "", 1) == "maybe"')

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    633,
 /**/
     632,
 /**/