patch 8.0.1218: writing to freed memory in autocmd

Problem:    Writing to freed memory in autocmd.
Solution:   Make a copy of the tag line. (Dominique Pelle, closes #2245)
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index 6ca3b22..aa7d157 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -249,6 +249,24 @@
   au! VimEnter
 endfunc
 
+func Test_BufReadCmdHelp()
+  " This used to cause access to free memory
+  au BufReadCmd * e +h
+  help
+
+  helpclose
+  au! BufReadCmd
+endfunc
+
+func Test_BufReadCmdHelpJump()
+  " This used to cause access to free memory
+  au BufReadCmd * e +h{
+  help
+
+  helpclose
+  au! BufReadCmd
+endfunc
+
 func Test_augroup_deleted()
   " This caused a crash before E936 was introduced
   augroup x