gnu: openssl: Set appropriate RUNPATH on shared libraries.

Fixes <http://bugs.gnu.org/20041>.
Reported by taylanbayirli@gmail.com (Taylan Ulrich Bayırlı/Kammer).

* gnu/packages/patches/openssl-runpath.patch: New file.
* gnu/packages/openssl.scm (openssl)[source]: Use it.
* gnu-system.am (dist_patch_DATA): Add it.