gnu: Add rust-nettle-sys-2.

* gnu/packages/crates-io.scm (rust-nettle-sys-2): New variable.
* gnu/packages/patches/rust-nettle-sys-disable-vendor.patch: New file.
* gnu/local.mk: Add it.

gnu: Add rust-zbase32-0.1.

* gnu/packages/crates-io.scm (rust-zbase32-0.1): New variable.

gnu: Add rust-webpki-roots-0.14.

* gnu/packages/crates-io.scm (rust-webpki-roots-0.14): New variable.

gnu: Add rust-webpki-roots-0.17.

* gnu/packages/crates-io.scm (rust-webpki-roots-0.17): New variable.

gnu: Add rust-webpki-roots-0.18.

* gnu/packages/crates-io.scm (rust-webpki-roots-0.18): New variable.

gnu: Add rust-webpki-0.18.

* gnu/packages/crates-io.scm (rust-webpki-0.18): New variable.

gnu: Add rust-webpki-0.21.

* gnu/packages/crates-io.scm (rust-webpki-0.21): New variable.

gnu: Add rust-want-0.2.

* gnu/packages/crates-io.scm (rust-want-0.2): New variable.

gnu: Add rust-untrusted-0.6.

* gnu/packages/crates-io.scm (rust-untrusted-0.6): New variable.

gnu: Add rust-tokio-test-0.2.

* gnu/packages/crates-io.scm (rust-tokio-test-0.2): New variable.

gnu: Add rust-tokio-rustls-0.12.

* gnu/packages/crates-io.scm (rust-tokio-rustls-0.12): New variable.

gnu: Add rust-tokio-mockstream-1.

* gnu/packages/crates-io.scm (rust-tokio-mockstream-1): New variable.

gnu: Add rust-tokio-named-pipes-0.1.

* gnu/packages/crates-io.scm (rust-tokio-named-pipes-0.1): New variable.

gnu: Add rust-tokio-macros-0.2.

* gnu/packages/crates-io.scm (rust-tokio-macros-0.2): New variable.

gnu: Add rust-tokio-buf-0.1.

* gnu/packages/crates-io.scm (rust-tokio-buf-0.1): New variable.

gnu: Add rust-tokio-0.2.

* gnu/packages/crates-io.scm (rust-tokio-0.2): New variable.

gnu: Add rust-term-0.2.

* gnu/packages/crates-io.scm (rust-term-0.2): New variable.

gnu: Add rust-string-0.2.

* gnu/packages/crates-io.scm (rust-string-0.2): New variable.

gnu: Add rust-spmc-0.3.

* gnu/packages/crates-io.scm (rust-spmc-0.3): New variable.

gnu: Add rust-skeptic-0.9.

* gnu/packages/crates-io.scm (rust-skeptic-0.9): New variable.