Move Lwt_process.redirection doc into the type

src/unix/lwt_process.mli

@@ -53,22 +53,17 @@ val shell : string -> command
 (** {3 Redirections} *)
 
 type redirection =
-    [ `Keep
-    | `Dev_null
-    | `Close
-    | `FD_copy of Unix.file_descr
-    | `FD_move of Unix.file_descr]
+    [ `Keep                     (** Point to the same file as in the parent. *)
+    | `Dev_null                 (** Redirect to [/dev/null] (POSIX) or [nul] (Win32). *)
+    | `Close                    (** Close the file descriptor. *)
+    | `FD_copy of Unix.file_descr (** Redirect to the file pointed to by [fd].
+                                      [fd] remains open in the parent.  *)
+    | `FD_move of Unix.file_descr (** Redirect to the file pointed to by [fd].
+                                      [fd] is then closed in the parent. *)
+    ]
 (** File descriptor redirections. These are used with the [~stdin], [~stdout],
     and [~stderr] arguments below to specify how the standard file descriptors
     should be redirected in the child process.
-
-    - [`Keep]: point to the same file as in the parent.
-    - [`Dev_null]: redirect to [/dev/null] (POSIX) or [nul] (Win32).
-    - [`Close]: close the file descriptor.
-    - [`FD_copy fd] redirect to the file pointed to by [fd]. [fd] remains open.
-    - [`FD_move fd] redirect to the file pointed to by [fd]. [fd] is then
-      closed.
-
     All optional redirection arguments default to [`Keep]. *)
 
 (** {3 Executing} *)