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: Tests using term_wait() can still be flaky.
Solution: Increase the wait time when rerunning a test. (James McCoy,
closes#5899) Halve the initial times to make tests run faster
when there is no rerun.
Problem: :let-heredoc does not trim enough.
Solution: Trim indent from the contents based on the indent of the first
line. Use let-heredoc in more tests.
Problem: Some balloon tests don't run when they can.
Solution: Split GUI balloon tests off into a separate file. (Ozaki Kiichi,
closes#4538) Change the feature check into a command for
consistency.
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: In a terminal 'ballooneval' does not work right away.
Solution: Flush output after drawing the balloon. Add the <Ignore> key
code. Add a test.
