This commit updates boost to version 1.77.0
More info about Boost 1.77.0 can be found at the usual place [1].

There are two new libraries in this version:
* Describe [2]: A C++14 reflection library, from Peter Dimov. Provides
macros for describing enumerators and struct/class members, and
primitives for querying this information.
* Lambda2 [3]: A C++14, dependency-free, single header lambda library, from
Peter Dimov. Allows simple function objects to be constructed via
expressions such as:
_1 + 5, _1 % 2 == 0, _1 > _2, or _1 == ' ' || _1 == '\t'.

[1]: https://www.boost.org/users/history/version_1_77_0.html
[2]: https://www.boost.org/libs/describe/
[3]: https://www.boost.org/libs/lambda2/

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

Missing braces.

Signed-off-by: Rosen Penev <rosenp@gmail.com>