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: 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: Tabs are not aligned when scrolling horizontally and a Tab doesn't
fit. (Axel Bender)
Solution: Handle a Tab as a not fitting character. (Christian Brabandt)
Also fix that ":redraw" does not scroll horizontally to show the
cursor. And fix the test that depended on the old behavior.
