Add --disable-openssl-version-check option

Add --disable-openssl-version-check option

Add "--disable-openssl-version-check" configure option, which removes
checking for vulnerable OpenSSL versions. It is supposed to be used by
downstream packagers and distributions who have other means to ensure
vulnerabilities are fixed, such as versioned package dependencies and
vulnerability handling processes.

This avoids the necessity of editing radiusd.conf on package upgrade to
make sure it keeps working. At the same time, it provides safe default
to those installing FreeRADIUS from source.

Instead of defining a dummy ssl_check_version function and ignoring
allow_vulnerable_openssl option, remove these altogether to match the
v3.0.x branch.