Merge branch 'ralf/select' into 'master'

use new select tactic from std++

See merge request !438
2 jobs for master in 19 minutes and 43 seconds (queued for 1 second)
Status Name Job ID Coverage
  Build
passed build-stdpp.dev-coq.8.11.1 #69669
fp

00:10:45

passed build-stdpp.dev-coq.dev #69670
fp

00:19:42