Problem:    All tab stops are the same.
Solution:   Add the variable tabstop feature. (Christian Brabandt,
            closes #2711)

Problem:    balloon_show() only works in terminal when compiled with the GUI.
Solution:   Add FEAT_BEVAL_GUI and refactor to move common code out of the GUI
            specific file.

Problem:    FEAT_WINDOWS adds a lot of #ifdefs while it is nearly always
            enabled and only adds 7% to the binary size of the tiny build.
Solution:   Graduate FEAT_WINDOWS.

Problem:    Some macros are in lower case, which can be confusing.
Solution:   Make a few lower case macros upper case.

Problem:    Typos in comments.
Solution:   Change "its" to "it's". (Matthew Brener, closes #1088)

Problem:    Modelines in source code are inconsistant.
Solution:   Use the same line in most files.  Add 'noet'.  (Naruhiko Nishino)

Problem:    Looping over windows, buffers and tab pages is inconsistant.
Solution:   Use FOR_ALL_ macros everywhere. (Yegappan Lakshmanan)

Problem:    Using old style function declarations.
Solution:   Change to new style function declarations. (script by Hirohito
            Higashi)

Problem:    EINTR is not always defined.
Solution:   Include errno.h in vim.h.