Implement crevice traits

[mtsr]

This implements crevice::AsStd140 for relevant types except BVec.

I wanted to check if something like this would be alright, before the remaining work:

• figuring out BVec
• adding the AsStd430 trait
• anything else you think should be done.

[bitshifter]

Need to specify the crates.io version here

[bitshifter]

It looks OK although I don't know what crevice is doing behind the scenes :)

[bitshifter]

I wouldn't want to merge until this can use crates.io, I assume they need to make a new release or something?

[LPGhatguy]

Hi, I'm the author of Crevice, I just found this while preparing a different PR!

I think that having math libraries depend on Crevice is tricky because of how domain-specific Crevice is. I have been working on two possible solutions to this problem, though:

• Use the IntoMint trait to support all math libraries automatically. I gave this a try in Support all math libraries using IntoMint LPGhatguy/crevice#38 and couldn't quite get it, but it might be possible with specialization.
• Support math libraries from Crevice using feature flags. This isn't so bad, I did this in Support math libraries manually LPGhatguy/crevice#37

If Crevice ends up manually supporting math libraries, it is likely that glam and cgmath will stay up to date, as they are the libraries that I use. It should be really easy for folks to PR upgrades to Crevice.

I would prefer that Crevice have to semver churn a little bit than make every math library do it for the sake of Crevice.

[bitshifter]

Going to close this as it's looking abandoned.