adding argon2 support to libcrypt. argon2 user authentication now
available via MKARGON2=yes (3 variants supported; argon2id recommended)
before using, please read argon2 paper at
https://github.com/P-H-C/phc-winner-argon2

Enable WARNS=4 by default for usr.bin, except for:
awk bdes checknr compile_et error gss hxtool kgetcred kinit
klist ldd less lex locale login m4 man menuc mk_cmds
mklocale msgc openssl rpcgen rpcinfo sdiff spell ssh
string2key telnet tn3270 verify_krb5_conf xlint

branches: 1.6.36;
more cleanups, WARNS=3

Use pw_gensalt() instead of using the cipher functions directly. Simplifies
the code a lot.

SRCS is not needed.

- use the gensalt functions from libcrypt instead of rolling our own.

Add support for SHA1 hashed passwords.
The algorithm used is essentially PBKDF1 from RFC 2898 but using
hmac_sha1 rather than SHA1 directly (suggested by smb@research.att.com).

* The format of the encrypted password is:
* $<tag>$<iterations>$<salt>$<digest>
*
* where:
* <tag> is "sha1"
* <iterations> is an unsigned int identifying how many rounds
* have been applied to <digest>. The number
* should vary slightly for each password to make
* it harder to generate a dictionary of
* pre-computed hashes. See crypt_sha1_iterations.
* <salt> up to 64 bytes of random data, 8 bytes is
* currently considered more than enough.
* <digest> the hashed password.

hmac.c implementes HMAC as defined in RFC 2104 and includes a unit
test for both hmac_sha1 and hmac_sha1 using a selection of the Known
Answer Tests from RFC 2202.

It is worth noting that to be FIPS compliant the hmac key (password)
should be 10-20 chars.

password hashing utility that allows des, md5 or bcrypt passwords to be
created in scripts; tool originally from downsj@openbsd.org;
approved by perry.