[ticket/11442] Do not suggest an option on ajax confirm box

Reverting commit cb13add269b78e1a9ac84a80c78557bb7695df09
Also fixing in prosilver and subsilver2

PHPBB3-11442
[ticket/11442] Use button name as indicator instead of css classes

This leaves it up to the style authors how to style any buttons, without
messing up any functionality.

PHPBB3-11442
Merge pull request #1391 from nickvergessen/ticket/11442

[ticket/11442] Use button name as indicator instead of css classes