This commit updates the boost package to version 1.70.0 [1] and updates the
Makefile to activate c++17 compile option.

This new Boost version brings two new header-only libraries:
Outcome: [2]
  A set of tools for reporting and handling function failures in contexts where
  directly using C++ exception handling is unsuitable, from Niall Douglas.

Histogram: [3]
  Fast and extensible multi-dimensional histograms with convenient interface
  for C++14, from Hans Dembinski.

More information about this release at the usual place [1].

[1]: https://www.boost.org/users/history/version_1_70_0.html
[2]: https://www.boost.org/libs/outcome/
[3]: https://www.boost.org/libs/histogram/

Signed-off-by: Carlos Ferreira <carlosmf.pt@gmail.com>