Problem: Various inconsistencies in test files.
Solution: Add modelines where they were missing. Use Check commands instead
of silently skipping over tests. Adjust indents and comments.
(Ken Takata, closes#6695)
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.
Problem: DirChanged is also triggered when the directory didn't change.
(Daniel Hahler)
Solution: Compare the current with the new directory. (closes#3697)
Problem: When a file gets a name when writing it 'acd' is not effective.
(Dan Church)
Solution: Invoke DO_AUTOCHDIR after writing the file. (Allen Haim, closes
#777, closes#803) Add test_autochdir() to enable 'acd' before
"starting" is reset.
