Purpose: Create simple dialog box asking user an either/or question.
On non-GUI setups or Matlab R2014b or later, it will ask a question
in the command window instead of showing a GUI dialog box.
History: 5/5/04 mpr decided whether or not to celebrate cinco de mayo
10/13/04 mpr set Yes Button automatically to be enlarged for large
1/21/05 mpr allowed fontsize to shrink for longer questions
1/27/05 mpr allowed question to break at file separator instead of
6/30/05 mpr orced underscores to remain as underscores instead of
3/27/06 mpr changed returned value to -1 when user deletes window;
note that this is dangerous because how a closed
window affects subsequent program behavior is not
implemented the same way in all code calling this
5/3/06 mpr set menubar to none for Version 2006a
8/25/06 mpr resized No Button as needed; could be done better, but
the plan is to keep the ‘Yes’ and ‘No’ strings short
so that the code doesn’t need to be pushed hard
9/29/06 mpr repainted buttons in version 7
1/14/07 mpr undid previoius fix because button color bug is almost
5/20/13 mk Add text only fallback for Octave and non-GUI.
11/05/15 mk Add GUI dialog for Octave in GUI mode. White-space cleanup.
7/20/17 mk Use text only fallback on Matlab R2014b and later.