Problem:    Compiler completion test fails when more scripts are added.
Solution:   Add a more generic pattern.

Problem:    Check for features implemented with "if".
Solution:   Use the Check commands. (Ken Takata, closes #7383)

Problem:    Compiler test fails on MS-Windows.
Solution:   Sort the found compiler plugin names.

Problem:    Compiler test depends on list of compiler plugins.
Solution:   Compare with the actual list of compiler plugins.

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:    Adding compiler plugin requires test change.
Solution:   Include compiler plugin and adjust test.

Problem:    The :compiler command causes a crash. (Daniel Steinberg)
Solution:   Do not use the script index if it isn't set.

Problem:    :helptags and some other functionality not tested.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #5567)

Problem:    Cannot build with +popupwin but without +quickfix. (John Marriott)
Solution:   Adjust #ifdefs.

Problem:    MSVC tests fail.
Solution:   Replace backslashes with slashes.