patch 8.1.1581: shared functions for testing are disorganised

Problem:    Shared functions for testing are disorganised.
Solution:   Group finctions in script files. (Ozaki Kiichi, closes #4573)
diff --git a/Filelist b/Filelist
index 63088a6..ff40389 100644
--- a/Filelist
+++ b/Filelist
@@ -124,6 +124,7 @@
 		src/testdir/shared.vim \
 		src/testdir/screendump.vim \
 		src/testdir/view_util.vim \
+		src/testdir/term_util.vim \
 		src/testdir/setup.vim \
 		src/testdir/gui_init.vim \
 		src/testdir/setup_gui.vim \