Improve build speed of dependencies

[tanzislam]

• [x] Fetch only necessary Boost submodules.
• [ ] Use yaSSL instead of OpenSSL, in order to reuse Crypto++.
• [x] Use curl instead of wget. (Much quicker to build in MacPorts.)

[tanzislam]

yaSSL didn't work out due to tight coupling with taocrypt and mySTL.