backend: Replace C pointer syntax with D

[dkorpel]

Seeing C syntax everywhere is one of things making backend code annoying to read. It's a lot of churn, but there's few open backend PRs currently, and master is going to be merged into stable soon, so this would be a convenient time to get this over with.

The only changes in this PR are removing and inserting spaces, nothing else.

[dlang-bot]

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Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#20726"