Log Message:
Update libsodium to 0.4.3, per maintainer update request by PR pkg/48260.

* Version 0.4.3
 - crypto_sign_seedbytes() and crypto_sign_SEEDBYTES were added.
 - crypto_onetimeauth_poly1305_implementation_name() was added.
 - poly1305-ref has been replaced by a faster implementation,
Floodyberry's poly1305-donna-unrolled.
 - Stackmarkings have been added to assembly code, for Hardened Gentoo.
 - pkg-config can now be used in order to retrieve compilations flags for
using libsodium.
 - crypto_stream_aes256estream_*() can now deal with unaligned input
on platforms that require word alignment.
 - portability improvements.