C client SSL implementation: request for initial review

- there are a couple of small TODO's, including a `BIO_free()` segfault in `riak_connection_free` (currently commented out)
- `test/ssl_tests/riak_c_client_ssl_tests.c` will be removed and better tests will be implemented
- once this is cleaned up a bit more, I'll submit an official PR
- you'll need the `autoconf-archive` package installed. If you are on OSX, I believe `brew install autoconf-archive` does the trick.

```
(cd test/ssl_tests && ./build_test_node.sh)
./autogen.sh
./configure -with-openssl=/usr/local/Cellar/openssl/1.0.1f
make
# edit test/ssl_tests/riak_c_client_ssl_tests.c with the path to the cacert file
./riak_ssl_test
```
Only tested on OSX at this point, Linux testing is next.

cc @javajolt @broach @bkerley