patch 8.1.1394: not restoring t_F2 in registers test

Problem:    Not restoring t_F2 in registers test.
Solution:   Assign to &t_F2 instead of t_F2. (Andy Massimino, closes #4434)
diff --git a/src/testdir/test_registers.vim b/src/testdir/test_registers.vim
index 1b8653e..3f4942e 100644
--- a/src/testdir/test_registers.vim
+++ b/src/testdir/test_registers.vim
@@ -162,7 +162,7 @@
   call assert_equal(['Quirk', 'Test', 'Quirk', 'Test'], getline(1, 4))
   bwipe!
   if exists('save_F2')
-    let t_F2 = save_F2
+    let &t_F2 = save_F2
   else
     set t_F2=
   endif
diff --git a/src/version.c b/src/version.c
index f774932..2d4c3c0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1394,
+/**/
     1393,
 /**/
     1392,