patch 8.1.0734: the hlsearch state is not stored in a session file

Problem:    The hlsearch state is not stored in a session file.
Solution:   Add "nohlsearch" if appropriate. (Jason Franklin)
diff --git a/src/testdir/test_mksession.vim b/src/testdir/test_mksession.vim
index fa08685..4d524da 100644
--- a/src/testdir/test_mksession.vim
+++ b/src/testdir/test_mksession.vim
@@ -198,6 +198,24 @@
   call delete('Xtest_mks.out')
 endfunc
 
+if has('extra_search')
+
+func Test_mksession_hlsearch()
+  set hlsearch
+  mksession! Xtest_mks.out
+  nohlsearch
+  source Xtest_mks.out
+  call assert_equal(1, v:hlsearch, 'session should restore search highlighting state')
+  nohlsearch
+  mksession! Xtest_mks.out
+  source Xtest_mks.out
+  call assert_equal(0, v:hlsearch, 'session should restore search highlighting state')
+  call delete('Xtest_mks.out')
+endfunc
+
+endif
+
+
 func Test_mksession_blank_windows()
   split
   split