Switch to crypto_api_chachapoly crate

This crate exposes both the ChaCha20Poly1305 IETF construction, and the
underlying ChaCha20 IETF primitive, removing the need for depending on
our own fork of the previous chacha20-poly1305-aead crate.

zcash_primitives/Cargo.toml

@@ -7,6 +7,7 @@ authors = [
 
 [dependencies]
 byteorder = "1"
+crypto_api_chachapoly = "0.1"
 ff = { path = "../ff" }
 hex = "0.3"
 lazy_static = "1"
@@ -18,7 +19,3 @@ sha2 = "0.8"
 [dependencies.blake2-rfc]
 git = "https://github.com/gtank/blake2-rfc"
 rev = "7a5b5fc99ae483a0043db7547fb79a6fa44b88a9"
-
-[dependencies.chacha20-poly1305-aead]
-git = "https://github.com/gtank/chacha20-poly1305-aead"
-rev = "aefc71f95e8bc43f2070e3c5b08130d9c86bbf4f"