* rb_libtorrent needs dev-libs/boost built with threads USE flag

!!! ERROR: net-libs/rb_libtorrent-0.12 failed.
Call stack:
  ebuild.sh, line 1630:   Called dyn_setup
  ebuild.sh, line 702:   Called qa_call 'pkg_setup'
  ebuild.sh, line 38:   Called pkg_setup
  rb_libtorrent-0.12.ebuild, line 30:   Called die