package/libxcrypt: new package

libxcrypt is a modern library for one-way hashing of passwords.  It
supports a wide variety of both modern and historical hashing methods:
yescrypt, gost-yescrypt, scrypt, bcrypt, sha512crypt, sha256crypt,
md5crypt, SunMD5, sha1crypt, NT.

Signed-off-by: Guillaume W. Bres <guillaume.bressaix@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>