Extend dladdr() for AIX, consequence from changes for openssl#6368.

The shared libraries are now stored as members of archives, as it is usual
on AIX. To correctly address this the custom dladdr()-implementation as
well as the dlfcn_load() routine need to be able to cope with such a
construct: libname.a(libname.so).

Signed-off-by: Matthias Kraft <Matthias.Kraft@softwareag.com>

Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6872)