Returns TRUE when morie's compiled .so was linked against libsodium
at install time (detected by ./configure via pkg-config --libs libsodium or a bare -lsodium probe). Nothing needs it: without it
ChaCha20-Poly1305, HKDF and the random bytes run on rmorie's native
code, with identical output. To use libsodium's code, install it and
reinstall morie:
