Keeps the boost libraries up to date. This also silences informational
messages that get spammed throughout the build, such as:
"Info: Boost.Config is older than your compiler version - probably
nothing bad will happen - but you may wish to look for an update Boost
version. Define BOOST_CONFIG_SUPPRESS_OUTDATED_MESSAGE to suppress this
message."
Which makes the compilation process a lot less noisy on Windows. It's
now much easier to actually spot warnings that occur.
