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:    Skipped tests are not properly listed.
Solution:   Throw a "Skipped" exception instead of using ":finish" or ":return".

Problem:    Too many #ifdefs.
Solution:   Graduate FEAT_MBYTE, the final chapter.

Problem:    No proper test for using 'termencoding'.
Solution:   Add a screendump test.  Fix using double width characters in a
            screendump.