Cygwin: enable the use of Dl_info and dladdr()

These weren't available in Cygwin at the time our DSO code was
written, but things have changed since.

Fixes #9385

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9402)

(cherry picked from commit 38f6f99cdf0a87345d646d30a764c089c38627ad)