patch 8.1.1476: no statistics displayed after running tests

Problem:    No statistics displayed after running tests.
Solution:   Summarize the test results. (Christian Brabandt, closes #4391)
            Also make it possible to report a skipped file.
diff --git a/src/testdir/test_arabic.vim b/src/testdir/test_arabic.vim
index d0211fe..450c6f9 100644
--- a/src/testdir/test_arabic.vim
+++ b/src/testdir/test_arabic.vim
@@ -3,7 +3,7 @@
 " functional tests that check the shaping works with real text.
 
 if !has('arabic')
-  finish
+  throw 'Skipped: arabic feature missing'
 endif
 
 source view_util.vim