Problem:    strcharpart() cannot include composing characters.
Solution:   Add the {skipcc} argument.

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

Problem:    Using the system default encoding makes tests unpredictable.
Solution:   Always use utf-8 or latin1 in the new style tests.  Remove setting
            encoding and scriptencoding where it is not needed.

Problem:    strcharpart() does not work properly with some multi-byte
            characters.
Solution:   Use mb_cptr2len() instead of mb_char2len(). (Hirohito Higashi)

Problem:    strgetchar() does not work correctly.
Solution:   use mb_cptr2len().  Add a test. (Naruhiko Nishino)

Problem:    Not testing utf-8 characters.
Solution:   Move the right asserts to the test_expr_utf8 test.

Problem:    Test fails when not using utf-8.
Solution:   Split test in regularand utf-8 part.