patch 8.1.0815: dialog for file changed outside of Vim not tested

Problem:    Dialog for file changed outside of Vim not tested.
Solution:   Add a test.  Move FileChangedShell test.  Add 'L' flag to
            feedkeys().
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 8ed4642..39b6889 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -121,6 +121,7 @@
 	test_feedkeys \
 	test_file_perm \
 	test_file_size \
+	test_filechanged \
 	test_fileformat \
 	test_filetype \
 	test_filter_cmd \
@@ -316,6 +317,7 @@
 	test_exit.res \
 	test_farsi.res \
 	test_file_size.res \
+	test_filechanged.res \
 	test_find_complete.res \
 	test_fixeol.res \
 	test_fnameescape.res \