message: [travis] Add Boost 1.64 to boost-builder
diff: set -eux
  -BOOST_VERSIONS=(1.58.0 1.59.0 1.60.0 1.61.0 1.62.0 1.63.0)
  +BOOST_VERSIONS=(1.58.0 1.59.0 1.60.0 1.61.0 1.62.0 1.63.0 1.64.0)
  BOOST_LIBRARIES="chrono,date_time,python,system,test,thread"
  BUILD_ROOT=/root/boosts
  