Stop old openssl extensions clashing with OpenSSL 3, add missing 2.7/3.0/3.1/3.2.0

[excid3]

Problem

After #12, Ruby 1.8.7, 1.9.3, 2.0.0 and 2.1.10 still segfault when pg is required before openssl (Bundler's usual order):

libcrypto.so.3(CRYPTO_set_ex_data) <- openssl.so  [BUG] Segmentation fault  (openssl/ssl.rb:71)

Their ext/openssl defines and exports its own X509_STORE_get_ex_data/X509_STORE_set_ex_data (and SSL_SESSION_cmp), and 1.8's digest/sha2 exports SHA256_Transform. With libpq's libcrypto.so.3 already loaded, calls to them bind to OpenSSL 3's real functions. --exclude-libs hides the bundled static OpenSSL, but not symbols the extension itself defines.

Fix

• New init_only_exports source patch (series 1.8–3.1): openssl and digest/{md5,sha1,sha2,rmd160} link with a version script exporting only Init_*. The flag goes into those extensions' Makefiles only, not rbconfig, so native gems are unaffected.
• check_openssl_hidden! now fails if those extensions export anything but Init_* (for patched series).
• Adds recipes for 2.7.0–2.7.7, 3.0.0–3.0.6, 3.1.0–3.1.6 and 3.2.0, which Hatchbox's S3 bucket has, so the fork can replace it.

Testing

Built locally with bin/package-linux (arm64): 1.8.7-p374, 2.1.10, 2.3.8, 3.1.7, 2.7.0, 3.0.0, 3.2.0 (both variants). All pass the package's own checks. Then on Ubuntu 24.04, each installed into ~/.asdf/installs/ruby/<v>, pg built from source against system libpq 16, in both require orders: pg to a TLS Postgres 17 (TLSv1.3) and Net::HTTPS to rubygems.org with peer verification. All pass (1.8.7 needs an explicit ca_file, as 1.8's net/http always has).

After merge

New versions release via release-new. Existing old-series versions need a dispatch of Release New Versions with only:
1.8.7-p374 1.9.3-p551 2.0.0-p648 2.1.10 2.2.10 2.3.8 2.4.10 2.5.9 2.6.10 2.7.8 3.0.7 3.1.7