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/runtest.vim b/src/testdir/runtest.vim
index 2a1b5ea..02d4d20 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -268,6 +268,9 @@
 else
   try
     source %
+  catch /^\cskipped/
+    call add(s:messages, '    Skipped')
+    call add(s:skipped, 'SKIPPED ' . expand('%') . ': ' . substitute(v:exception, '^\S*\s\+', '',  ''))
   catch
     let s:fail += 1
     call add(s:errors, 'Caught exception: ' . v:exception . ' @ ' . v:throwpoint)