Remove embedded luasocket and prepare proper linking

Hi everyone,

This is the second of two pull requests (the first [being against luasocket](https://github.com/diegonehab/luasocket/pull/72)). Please read the linked luasocket pull request for all the details, I'll give a short summary here.

With the two fixes, it is possible to properly use luasec and luasocket without the duplicated code in the luasec repository. Luasocket has been modified to export the required symbols. This should fix any issues which arose, arise and will in future arise from inconsistency between luasec and luasocket.

If you have any suggestions for improvements or any kind of critique, please let me know so that we can fix that quickly.

best regards,
Jonas