Add pointer lints, run clippy, apply fixes

[urschrei]

We're now denying some optional lints related to unsafe handling of raw pointers

[urschrei]

Hmm where is this pkg-config error coming from on macOS

https://github.com/georust/proj/actions/runs/4233808378/jobs/7355244018

[michaelkirk]

Hmm where is this pkg-config error coming from on macOS

I opened https://github.com/georust/proj/pull/152 in at attempt to fix it. Let's see what CI says.

[urschrei]

Bors try

[bors[bot]]

try

Build succeeded:

• ci result

[urschrei]

bors r=lnicola

[bors[bot]]

Build succeeded:

• ci result