ruby: make from_ruby call apply_changes_from_converted_types on the returned value

It is assumed that the value returned by from_ruby can be used
as a typelib value, i.e. directly on a C++ interface. However,
if apply_changes_from_converted_types does not get called, the
underlying C++ structure is not up-to-date (and therefore the
assumption is broken)
ruby: do not override custom convertions to/from Hash and Array by the default ones