Mac: Enable accelerator key functionality

[hoffie]

Just found this in the Qt docs:

On Mac, shortcuts are disabled by default. Call qt_set_sequence_auto_mnemonic() to enable them. However, because mnemonic shortcuts do not fit in with Aqua's guidelines, Qt will not show the shortcut character underlined.

We should probably consider activating them on Mac, too?
cc @softins @ann0see

Originally posted by @hoffie in #1693 (reply in thread)

[softins]

For 3.8.0? Or after that, ready for the next release?

[hoffie]

For 3.8.0? Or after that, ready for the next release?

Next release, I'd say. It does look minor, but nobody has tested it yet. This is not a regression or something with huge demand either.

[HughePaul]

This is not a regression or something with huge demand either.

How do I register that this is in huge demand?