README: document dbus_message_new
src/message.c: Make DBusMessageIter argument to message_iter_init optional, now retuns iter object on success, or nil on failure
src/message_iter.c: Fix incorrect argument indexes in error messages
README: Document args of dbus_message_iter_init*
src/message_iter: Add iter:clone() method
src/ldbus.c: Add basic_types table
README: document ldbus.types and ldbus.basic_types
src/message*: #define DBUS_MESSAGE_ITER_METATABLE "ldbus_DBusMessageIter"
src/message_iter.c: Return nil for INVALID from iter:get_arg_type()
src/message/variant: Initial commit

A simple class to abstract variants for packing/unpacking
src/connection.c: Push nil on error (not false)