patch 8.1.1228: not possible to process tags with a function

Problem:    Not possible to process tags with a function.
Solution:   Add tagfunc() (Christian Brabandt, Andy Massimino, closes #4010)
diff --git a/src/testdir/test_alot.vim b/src/testdir/test_alot.vim
index 47fe5be..a7db66a 100644
--- a/src/testdir/test_alot.vim
+++ b/src/testdir/test_alot.vim
@@ -60,6 +60,7 @@
 source test_tabline.vim
 source test_tabpage.vim
 source test_tagcase.vim
+source test_tagfunc.vim
 source test_tagjump.vim
 source test_taglist.vim
 source test_timers.vim