MINOR: lua: move class registration facilities

The functions
 - hlua_class_const_int()
 - hlua_class_const_str()
 - hlua_class_function()
are use for common class registration actions.

The function 'hlua_dump_object()' is generic dump name function.

These functions can be used by all the HAProxy objects, so I move
it into the safe functions file.
diff --git a/include/proto/hlua_fcn.h b/include/proto/hlua_fcn.h
index 179d40c..560d1f4 100644
--- a/include/proto/hlua_fcn.h
+++ b/include/proto/hlua_fcn.h
@@ -1,7 +1,11 @@
 #ifndef _PROTO_HLUA_FCN_H
 #define _PROTO_HLUA_FCN_H
 
+void hlua_class_const_int(lua_State *L, const char *name, int value);
+void hlua_class_const_str(lua_State *L, const char *name, const char *value);
+void hlua_class_function(lua_State *L, const char *name, int (*function)(lua_State *L));
 void *hlua_checkudata(lua_State *L, int ud, int class_ref);
 int hlua_fcn_reg_core_fcn(lua_State *L);
+int hlua_dump_object(lua_State *L);
 
 #endif /* _PROTO_HLUA_FCN_H */