changes for dynload for macOS and OpenBSD: - reverted last commit, b/c of brainfat (wrongly assuming all libs iterated over are opened by dynload) - make use of RTLD_NOLOAD, though, when re-dlopen-ing to get path, for performance (where available)

Daniel Adler <dadler@uni-goettingen.de>
Tassilo Philipp <tphilipp@potion-studios.com>
Olivier Chafik <olivier.chafik@gmail.com>
Erik Mackdanz <erikmack@gmail.com>
Masanori Mitsugi <mitsugi@linux.vnet.ibm.com>