Add camlp4 dependency after r385012 uncovered by r385413

devel/ocaml-lwt (4 skipped) is still broken by another issue:

File "src/top/toplevel.ml", line 60, characters 17-62:
Error: This expression has type load:bool -> Path.t
       but an expression was expected of type 'a * 'b

PR: 199845
Reported by: pkg-fallout
Approved by: portmgr blanket