Add '-lssp' linker flag for Solaris. Check for libraries after host specific setup.
Disable compiler warning for Solaris
declare z85_encode / decode in zmq_utils

they are used by curve_keygen, but not available
include missing platform.hpp in curve_keygen

it was excluded, so HAVE_SODIUM would never be defined,
leading to curve_keygen always reporting "recompile with libsodium"
config for libsodium in alternate path, using CPP flags for both C and C++ sources.
Fixed merge conflict error
Merge pull request #12 from hintjens/master

Backporting fixes from master