ext/ladspa/gstladspa.c: Don't use GST_BOILERPLATE as the stuff generated from it...

ext/ladspa/gstladspa.c: Don't use GST_BOILERPLATE as the stuff generated from it is not used anyway and can't be used.

Original commit message from CVS:
* ext/ladspa/gstladspa.c: (gst_ladspa_base_init),
(gst_ladspa_class_init), (ladspa_describe_plugin), (plugin_init):
Don't use GST_BOILERPLATE as the stuff generated from it is not used
anyway and can't be used.
Store the class struct of the correct type in parent_class.
Pass the LADSPA_Descriptor as class_data to the class_init function
as preparation for the time, when we can add pad templates and friends
in class_init and add a FIXME for that.
Don't use a custom hash table for passing the LADSPA_Descriptors to
base_init but use g_type_set_qdata and g_type_get_qdata.