bug#60646: 28.2; delete-selection-mode

[Drew Adams]

> I would like to express my strong support
> for enabling delete-selection-mode by default.
> This is standard for almost all other text
> applications and feels unintuitive not to have it.

+1.  I've advocated the same for decades.

This should have happened when we turned on
`transient-mark-mode' by default.  And both
of those default-behavior changes should
really have happened long before that.