configure: check if &errno is thread-local for OpenSSL

This is step one for fixing, or at least mitigating, PR60947. Determine
which platforms can use the default OpenSSL (1.0.x) threadid-callback,
by recording the address of errno for several threads and testing that
they're all different.

The result of this test is put into the new macro,
AP_OPENSSL_USE_ERRNO_THREADID.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/trunk-openssl-threadid@1791054 13f79535-47bb-0310-9956-ffa450edef68