tal: add tal_dup_or_null and tal_dup_talarr helpers.
[ccan] / ccan / crypto /
drwxr-xr-x   ..
drwxr-xr-x - hkdf_sha256
drwxr-xr-x - hmac_sha256
drwxr-xr-x - ripemd160
drwxr-xr-x - sha256
drwxr-xr-x - sha512
drwxr-xr-x - shachain
drwxr-xr-x - siphash24
drwxr-xr-x - xtea