Use old clippy attributes syntax

[stanislav-tkach]

As far as I can see, "old" syntax works both with nightly and stable clippy.

Closes #561.

[DoumanAsh]

@fafhrd91 I don't use clippy at all, is it fine to update?

[mehcode]

The new syntax is stable in 1.30 which was released today.

[stanislav-tkach]

@mehcode Unfortunately, it isn't that simple:

$ rustc --version
rustc 1.30.0 (da5f414c2 2018-10-24)
$ rustup --version
rustup 1.14.0 (1e51b07cc 2018-10-04)
$ cargo --version
cargo 1.30.0 (36d96825d 2018-10-24)
...
error[E0658]: scoped lint `clippy::needless_pass_by_value` is experimental (see issue #44690)

https://travis-ci.com/exonum/exonum/jobs/154392451#L2159

[mehcode]

Ah. I was confused because of rust-lang/rust#55331

Seems it won't be stable until 1.31

[codecov]

Codecov Report

Merging #562 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master     #562   +/-   ##
=======================================
  Coverage   76.23%   76.23%           
=======================================
  Files         103      103           
  Lines       16825    16825           
=======================================
  Hits        12826    12826           
  Misses       3999     3999

Impacted Files	Coverage Δ
src/httpresponse.rs	83.24% <ø> (ø)	⬆️
src/server/output.rs	67.96% <ø> (ø)	⬆️
src/server/http.rs	58.58% <ø> (ø)	⬆️
src/info.rs	92.78% <ø> (ø)	⬆️
src/server/h2writer.rs	47.79% <ø> (ø)	⬆️
src/ws/frame.rs	76.47% <ø> (ø)	⬆️
src/scope.rs	92.8% <ø> (ø)	⬆️
src/ws/mask.rs	89.83% <ø> (ø)	⬆️
src/client/writer.rs	69.63% <ø> (ø)	⬆️
src/middleware/defaultheaders.rs	72.97% <ø> (ø)	⬆️
... and 1 more

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[DoumanAsh]

@fafhrd91 I merged since old syntax should work with both versios