community/libtorrent-rasterbar: use c++17
Patchset from Wolf wolf@wolfsden.cz via aports #3772:
libtorrent-rasterbar segfaults when using the default c++ standard (14)
in 3.15. There is a upstream bug report [0] stating that using 17 fixes the
crash, and I can confirm that is the case for me as well.
Reported upstream [1].
0: https://github.com/arvidn/libtorrent/issues/6028
1: https://github.com/arvidn/libtorrent/issues/6567