Implement Don't Escape feature for db engine

[lonnieezell]

Add in missing don't escape feature that seemed to be missing since the original DB refactor.

Fixes #1667

[vlakoff]

On a related note, I don't really understand the comment here:

While it might be nicer to have named keys for our binds array
with PHP 7+ we get a huge memory/performance gain with indexed
arrays instead, so lets take advantage of that here.

... as these array keys are still named keys (e.g. "foobar", "foobar.2", "foobar.3", etc)

We could easily switch to numeric keys. But would it cause BC issues?

Refs: PHP 7 performance improvements (1/5): Packed arrays