http: Fix overlooked agent.globalAgent export

Noticed by @bnoordhuis in https://github.com/joyent/node/pull/5991#discussion_r5575946
https: fix default port

https.get('https://github.com/') should use port 443, not 80.
test: Move test-http-default-port from disabled to simple
build: embed the mdb_v8.so into the binary

This builds and includes the mdb_v8.so in the binary of node so mdb
can be sure to always use the latest version