Fix Clippy lints

[GabrielMajeri]

This PR attempts to get CI working again by fixing some of the reported Clippy lints.

The biggest issue has been caused by the use_self lint, which recommends using the Self type where possible. However, it has a known limitation when used with generic code and / or associated types. So for now, it is disabled on the whole packed_simd crate.

[gnzlbg]

Looks like the benchmarks are failing because ispc-rs fails to find ispc in the PATH, cc @Twinklebear did anything changed in ispc-rs upstream about this ? I see some "recent" comments about "path" there https://github.com/Twinklebear/ispc-rs/commits/master

[Twinklebear]

Interesting, I haven't changed the path handling inside ispc-rs itself, sorry about the bad commit messages. In those I was trying to get ispc setup in Travis to build the examples for testing (https://github.com/Twinklebear/ispc-rs/blob/master/.travis.yml#L16-L24).

From looking at the CI log it does look like ispc is in the path (also b/c this doesn't print out https://github.com/rust-lang-nursery/packed_simd/blob/master/ci/benchmark.sh#L19). It looks like the benchmarks do succeed on Linux, one possible issue is that I don't have a Mac (and didn't setup Travis to run for OS X), so if there's some OS X specific issue I won't see it. Let me get setup with an OS X CI build on Travis and have a look.

[gnzlbg]

Interesting, I haven't changed the path handling inside ispc-rs itself

That's really helpful, maybe we just aren't passing the PATH properly to our benchmarking scripts anymore, will have to track which change on our side broke this. EDIT: as you mentioned, ispc appears to be in the PATH, weird =/ I have a macosx machine, will try to reproduce this locally.

Let me know if you need any help setting OSX CI for ispc-rs!

[Twinklebear]

@gnzlbg were you able to reproduce this? I've added a CI runner for OS X in Twinklebear/ispc-rs@5d2a62b and the examples do look to be building successfully (https://travis-ci.org/Twinklebear/ispc-rs/jobs/480030331)

[gnzlbg]

Not really, I've ended up allowing travis to fail on macosx for the time being =/