Merge branch 'ilocked' into 'master'

Introduce a connective `ilocked` to stop `iNext` and `iFrame`.

See merge request FP/iris-coq!67
3 jobs for master in 2 minutes and 59 seconds (queued for 1 second)
Status Name Job ID Coverage
  Build
passed build-coq8.6.1 #3813
fp-timing

00:02:44

passed build-coq8.7 #3812
fp-timing

00:02:44

 
  Opam
passed opam #3814

00:00:13