Fix 'hidden lifetime parameters in types are deprecated'

[Enselic]

I am messing around with Rust's standard library and gimli. In my particular setup, Rust's build system tries to build gimli in a way that can be simulated like this:

cargo rustc --  -Wrust_2018_idioms -Wunused_lifetimes -Dwarnings

When build that way, the master branch fails with a bunch of errors like this:

error: hidden lifetime parameters in types are deprecated

This PR fixes that.

[philipc]

I'm still not convinced this is useful for parameters (which is the bulk of this PR), but I guess that ship has sailed.

Since you've gone to the effort of changing this, I assume that you want this to continue to work, so

gimli/src/lib.rs

Line 27 in c49f64d

//#![warn(elided_lifetimes_in_paths)]

should be changed to help check that.

Also it appears that other targets such as tests need fixing still.

[Enselic]

Thanks for review. I have now enabled it as a warning and also updated tests (so that there is no warning emitted when running cargo test).