Compilation failure since OpenSSL (alpha 13)

[stac47]

Hello,
I am building poco (latest) with gcc11 on Unbuntu 20.10 and I try to build Poco with OpenSSL3. The Poco build fails since OpenSSL alpha 13 with the following error message:

/BUILD/poco-1.10.1-all/Crypto/src/RSACipherImpl.cpp:54:32: error: 'RSA_SSLV23_PADDING' was not declared in this scope; did you mean 'RSA_NO_PADDING'?
   54 |                         return RSA_SSLV23_PADDING;
      |                                ^~~~~~~~~~~~~~~~~~
      |                                RSA_NO_PADDING

The reason is the following commit in OpenSSL:

commit b0aae913246af1d07e728d24f53f55028f61c696
Author: Rich Salz <rsalz@akamai.com>
Date:   Mon Feb 22 12:55:25 2021 -0500

    Remove RSA SSLv23 padding mode

    Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
    Reviewed-by: Tomas Mraz <tomas@openssl.org>
    (Merged from https://github.com/openssl/openssl/pull/14248)

[obiltschnig]

Probably also time to remove SSL2/3 support from POCO altogether.