Replace Pervasives.* with Stdlib.*

Since OCaml 4.07 (released 2018-07-10) the always-loaded standard
library module has been called Stdlib.  The old Pervasives module was
finally removed in OCaml 5.

$ perl -pi.bak -e 's/Pervasives\./Stdlib./g' -- `git ls-files`

OCaml >= 4.07 is now required.

Also update the common submodule with:

  commit d61cd820b49e403848d15c5deaccbf8dd7045370
  Author: Jürgen Hötzel
  Date:   Sat May 20 18:16:40 2023 +0200

    Add support for OCaml 5.0

daemon/chroot.ml

@@ -51,7 +51,7 @@ let f t func arg =
     try
       let chan = out_channel_of_descr wfd in
       output_value chan ret;
-      Pervasives.flush chan;
+      Stdlib.flush chan;
       Exit._exit 0
     with
       exn ->

docs/guestfs-building.pod

@@ -119,7 +119,7 @@ virt tools which are still written in Perl.
 
 I<Required>.  Part of Perl core.
 
-=item OCaml E<ge> 4.04
+=item OCaml E<ge> 4.07
 
 =item OCaml findlib
 

generator/pr.ml

@@ -25,7 +25,7 @@ open Std_utils
 open Utils
 
 (* Output channel, 'pr' prints to this. *)
-let chan = ref Pervasives.stdout
+let chan = ref Stdlib.stdout
 
 (* Number of lines generated. *)
 let lines = ref 0
@@ -53,7 +53,7 @@ let output_to ?(perm = 0o444) filename k =
   chan := open_out filename_new;
   k ();
   close_out !chan;
-  chan := Pervasives.stdout;
+  chan := Stdlib.stdout;
 
   (* Is the new file different from the current file? *)
   if Sys.file_exists filename && files_equal filename filename_new then

m4/guestfs-ocaml.m4

@@ -38,10 +38,10 @@ AC_ARG_ENABLE([ocaml],
     [],
     [enable_ocaml=yes])
 
-dnl OCaml >= 4.04 is required.
-ocaml_ver_str=4.04
+dnl OCaml >= 4.07 is required.
+ocaml_ver_str=4.07
 ocaml_min_major=4
-ocaml_min_minor=4
+ocaml_min_minor=7
 AC_MSG_CHECKING([if OCaml version >= $ocaml_ver_str])
 ocaml_major="`echo $OCAMLVERSION | $AWK -F. '{print $1}'`"
 ocaml_minor="`echo $OCAMLVERSION | $AWK -F. '{print $2}' | sed 's/^0//'`"