net-p2p/libtorrent: Update to 0.13.7

• IPv6 is not a configure option anymore.
• Remove outdated patches.
• Remove CONFLICTS, rblibtorrent moved to libtorrent-rasterbar and libtorrent does not conflict with it.
• Reset maintainer, three timeouts.

PR: 229553
Reported by: tj@mrsk.me (email)
Approved by: maintainer timeout (pipfstarrd@openmailbox.org, > 2 weeks)