libpng: make sure libpng15.{a,so} is available for cross-compiling.
wget: version bump to 1.15
openssl: fix doc generation on systems with very recent versions of perl.

See: https://gist.github.com/martensms/10107481, https://github.com/openssl/openssl/issues/57
gcc: ensure we get a libstdc++.so, without missing symbols. Also, now we get a libssp.so. Yay!