[OpenSSL-3.0LTS] DES API marked as obsolete(OSSL_DEPRECATEDIN_3_0) brokes building libtelnet

[Takehiko NOZAKI]

see Issue #151, Issue #152 and Issue #180

‌

[Takehiko NOZAKI]

RFC2953 Telnet encryption

[Takehiko NOZAKI]

to fix this problem:

1. define OSSL_DEPRECATEDIN_3_0 and use OpenSSL libcrypto’s DES implementation
2. revive libdes
3. libtelnet use own des implementation

‌

I think 3. is the solution.

[Takehiko NOZAKI]

more over, I think telnet DES encryption is considered obsolete and harmful.

‌

better to move RFC9266 Channel Bindings for TLS 1.3

[Takehiko NOZAKI]

O*BSD has already dropped libexec/telnetd and lib/libtelnet, usr.bin/telnet exists but des encryption is dropped too.