patch 8.1.0496: no tests for indent files

Problem:    No tests for indent files.
Solution:   Add a mechanism for running indent file tests.  Add a first test
            for Vim indenting.
diff --git a/Filelist b/Filelist
index 3052d75..117f0fa 100644
--- a/Filelist
+++ b/Filelist
@@ -691,6 +691,11 @@
 		runtime/compiler/README.txt \
 		runtime/indent/*.vim \
 		runtime/indent/README.txt \
+		runtime/indent/Makefile \
+		runtime/indent/testdir/README.txt \
+		runtime/indent/testdir/*.vim \
+		runtime/indent/testdir/*.in \
+		runtime/indent/testdir/*.ok \
 		runtime/ftplugin/*.vim \
 		runtime/ftplugin/logtalk.dict \
 		runtime/ftplugin/README.txt \