patch 8.0.1377: cannot call a dict function in autoloaded dict

Problem:    Cannot call a dict function in autoloaded dict.
Solution:   Call get_lval() passing the read-only flag.
diff --git a/src/testdir/test_autoload.vim b/src/testdir/test_autoload.vim
new file mode 100644
index 0000000..a92851f
--- /dev/null
+++ b/src/testdir/test_autoload.vim
@@ -0,0 +1,11 @@
+" Tests for autoload
+
+set runtimepath=./sautest
+
+func! Test_autoload_dict_func()
+  let g:loaded_foo_vim = 0
+  let g:called_foo_bar_echo = 0
+  call g:foo#bar.echo()
+  call assert_equal(1, g:loaded_foo_vim)
+  call assert_equal(1, g:called_foo_bar_echo)
+endfunc