[kernel] export Dynamic.load_packages

`Dynamic.load_module` does not know about Findlib's subpackages 

src/kernel_services/plugin_entry_points/dynamic.mli

@@ -149,9 +149,14 @@ end
 (** {2 Dynamically Loaded Modules} *)
 (* ************************************************************************* *)
 
-val load_module: string -> unit
+(** loads a list of Findlib packages
+    @since Frama-C+dev
+*)
+val load_packages: string list -> unit
+
 (** Load the module specification. See -load-module option.
     @modify Magnesium-20151001 new API. *)
+val load_module: string -> unit
 
 (** Sets the load path for modules in FRAMAC_PLUGIN, prepending it with [path].
     Does not load any plugins.
@@ -159,7 +164,9 @@ val load_module: string -> unit
     @since Phosphorus-20170501-beta1. *)
 val set_module_load_path : string list -> unit
 
-(** [is_loaded package] returns [true] iff [package] has already been loaded.*)
+(** [is_loaded package] returns [true] iff [package] has already been loaded.
+    @since Frama-C+dev
+*)
 val is_loaded: string -> bool
 
 (**/**)