WIP: Update libsignal-protocol

• Depends on https://github.com/Michael-F-Bryan/libsignal-protocol-rs/issues/55 ;
• Remove [patch.crates-io] section and squash when that gets resolved.
• scrypt 0.3.0 is out 2045314f is on master
• qmetaobject has a useful update pending https://github.com/woboq/qmetaobject-rs/pull/59, although it shouldn't block this MR and can be postponed.
• Wait for libsignal 0.1.1 to be released, regenerate Cargo.lock, and cross fingers for CI to turn green!

This patch should shrink the executable size quite a bit, because of some duplicated transitive dependencies. It also gets rid of the deprecated rust-crypto/scrypt library in favour op the upstream one.