Investigate vendor prefixes still needed

[JohannesDoberer]

Investigate whether vendor prefixes are still needed or which ones we can get rid of.

[walmazacn]

The following CSS properties are included in source CSS files and have some prefixes - some of them don't need it anymore, but other still do (according to "caniuse.com"):

• 'animation' - no prefixes
• 'appearance' - no prefixes
• 'border-radius' - no prefixes
• 'box-shadow' - no prefixes
• 'font-smoothing' - moz, webkit
• 'keyframes' - no prefixes
• 'overflow-scrolling' - webkit
• 'scrollbar' - webkit
• 'text-size-adjust' - webkit
• 'text-stroke' - webkit
• 'transform' - no prefixes
• 'transition' - no prefixes
• 'user-select' - webkit

[walmazacn]

This task should be handled after another one - #3824