Problem:    MS-Windows: system test may fail if more.exe is installed.
Solution:   Explicitly use more.com. (Taro Muraoka, Ken Takata, closes #6517)

Problem:    Various code not fully tested.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes #6049)

Problem:    MS-Windows: testing external commands can be improved.
Solution:   Adjust tests, remove duplicate test. (closes #4928)

Problem:    MS-Windows: shell commands fail if &shell contains a space.
Solution:   Use quotes instead of escaping. (closes #4920)

Problem:    MS-Windows: system() test fails.
Solution:   Expect CR when using systemlist().

Problem:    MS-Windows: redirect in system() does not work.
Solution:   Handle 'shellxescape' and 'shellxquote' better. (Yasuhiro
            Matsumoto, closes #2054)

Problem:    Inconsistently using GetVimCommand() and v:progpath. (Daniel
            Hahler)
Solution:   Use GetVimCommand(). (closes #4806)

Problem:    More functions can be used as a method.
Solution:   Add has_key(), split(), str2list(), etc.

Problem:    Test files still use function!.
Solution:   Remove the exclamation mark.  Fix overwriting a function.

Problem:    System test failing when using X11 forwarding.
Solution:   Set $XAUTHORITY before changing $HOME. (closes #1812)
            Also use a better check for the exit value.