Updates for buttons changes in core
Updates for input-to-button and styling changes in core in 5.31, including also that using button text to determine the clicked button doesn't work anymore.
Also a hovering inconsistency.
Also addresses #107 (closed) regarding the leaf disappearing which broke in an earlier version.
Note there's changes both with and without popup forms enabled.
I'm not sure about the use of min-height, but that's what was used before. Should probably check various browsers.