Remove MKCRYPTO_RC5. Unconditionally include RC5 in libcrypto.so.
This option existed only because RC5 is covered by patents that, twenty
years ago, we had reason to suspect the patent holder, RSA, Inc., might
litigate. The two US patents in question are 5,724,428 and 5,835,600.
According to the USPTO Patent Term Calculator web site at
<https://www.uspto.gov/patent/laws-and-regulations/patent-term-calculator#heading-5>
(retrieved 2017-05-21), patents filed after 1995-06-07 expire twenty
years after the filing date.
number filing date
5,724,428 1995-11-01
5,835,600 1997-04-21
Thus, these patents appear to be expired.
As proposed on tech-crypto and tech-security:
https://mail-index.netbsd.org/tech-crypto/2017/05/05/msg000718.html
https://mail-index.netbsd.org/tech-security/2017/05/05/msg000927.html
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