Adds a pad template to an element class based on the static pad template
@templ. This is mainly used in the _class_init functions of element
implementations. If a pad template with the same name already exists,
the old one is replaced by the new one.
Adds a pad template to an element class based on the static pad template @templ. This is mainly used in the _class_init functions of element implementations. If a pad template with the same name already exists, the old one is replaced by the new one.