Remove most of the RSA_FLAG_SIGN_VER documentation

ok jsing kn

Document RSA_get0_* for individual RSA members.

Loosely based on OpenSSL commit 6692ff77.

Prodded by job

explain the acronym "CRT"; suggested by tb@

document the RSA_FLAG_* constants for RSA_*_flags(3);
OK tb@ jmc@

finish crypto HISTORY; mostly 1.1.0/6.3, but also various other fixes

In rsa.h rev. 1.37 2018/02/20 17:42:32, tb@ provided
RSA_clear_flags(3), RSA_test_flags(3), and RSA_set_flags(3).
Merge the documentation, tweaked by me.

In rsa.h rev. 1.34 2018/02/18 12:53:46, tb@ provided RSA_get0_factors(3)
and RSA_set0_factors(3) and in rev. 1.36 2018/02/18 12:57:14
RSA_get0_crt_params(3) and RSA_set0_crt_params(3).
Merge the docu

In rsa.h rev. 1.34 2018/02/18 12:53:46, tb@ provided RSA_get0_factors(3)
and RSA_set0_factors(3) and in rev. 1.36 2018/02/18 12:57:14
RSA_get0_crt_params(3) and RSA_set0_crt_params(3).
Merge the documentation from OpenSSL.

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Merge documentation for {DH,DSA}_get0_{key,pqg}(3),
EVP_PKEY_get0_{DH,DSA,RSA}(3), and RSA_{g,s}et0_key(3)
that tb@ just provided.