Problem:    Dropping files is ignored while Vim is busy.
Solution:   Postpone the effect of dropping files until it's safe.

Problem:    Lose contact with jobs when :gui forks.
Solution:   Don't fork when there is a running job. Make log message for a
            died job clearer.  Also close the terminal when stderr and stdout
            are the same FD.

Problem:    When using 'termguicolors' SpellBad doesn't show.
Solution:   When the GUI colors are not set fall back to the cterm colors.

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:    Strike-through text not supported.
Solution:   Add support for the "strikethrough" attribute. (Christian
            Brabandt, Ken Takata)

Problem:    Compiler warnings with Solaris Studio when using GTK3.
Solution:   Define FUNC2GENERIC depending on the system. (Kazunobu Kuriyama)

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

Problem:    Generating prototypes with Cygwin doesn't work well.
Solution:   Change #ifdefs. (Ken Takata)

Problem:    Color handling of X11 GUIs is too complicated.
Solution:   Simplify the code.  Use RGBA where appropriate. (Kazunobu
            Kuriyama)