ppx_metaquot: Pervasives is deprecated on 4.08

[aantron]

Metaquot generates Pervasives.(!) in its output code when metaloc is not used:

ppx_tools_versioned/ppx_metaquot_407.ml

Line 195 in c73ed55

let loc = ref (app (evar "Pervasives.!") [evar "Ast_helper.default_loc"])

Compiling this code then results in warnings like this on 4.08:

File "_none_", line 1:
Error (alert deprecated): module Stdlib.Pervasives
Use Stdlib instead.

If you need to stay compatible with OCaml < 4.07, you can use the
stdlib-shims library: https://github.com/ocaml/stdlib-shims