Move 'Arguments: clear implicits' to 2.7.4 (Close 2891)
Goal printing made uniform: always done in STM (close 3585)

Goal printing was partially broken.  Some commands in vernacentries
were printing, but not all of them.  Moreover an unlucky combination
of `Flags.verbosely (fun () -> interp "Set Silent")` was making the
silent flag not settable anymore.

Now STM always print the open goals after a command when run in interactive
mode via coqtop or emacs.  More modern GUI do ask for the goals.
Fix the way lexeme start is computed (Close 3737)