bug#56691: outline-minor-mode displays navigation arrow buttons as emojis

[Paul W. Rankin]

Summary:

First discovered in the describe-bindings buffer (C-h b). Screenshot: 
http://0x0.st/ojN5.png

Buffers using outline-minor-mode will attempt to add navigation arrow 
buttons (i.e. show/hide) displaying emojis instead of arrows or text 
representation.

This occurs even when widget-image-enable => nil.

Appears to be introduced in commit 
3a855c5dac1b5cc42ee57cebed0323d591b54c68

Steps to reproduce:

1. $emacs -Q
2. C-h b

Expected results:

Buffer navigation arrows are arrows.

Actual results:

Buffer navigation arrows are emojis.

Notes for the committer:

Do not use emojis in software designed for adults; what you see as 
whimsical appears to others as childish and unprofessional. While I 
cannot speak for vision-impaired users, this also raises the issue of 
whether emojis appropriated for functional use create yet another 
difficulty for those requiring screen readers.

As always, if you wish to add a feature to Emacs (i.e. not fix a bug) -- 
do not make that new feature enabled by default! This is incredibly 
rude. Document the feature and allow others to make their own choices.