utils: expose pad_link_maybe_ghosting

utils: expose pad_link_maybe_ghosting

This is a useful function to automatically add ghost pads when linking
two elements across bin boundaries without know their exact parentage.

e.g. when using gst_parse_bin_from_description (with or without it ghosting pads),
one can simply retreive the src/sink pads from the bin to link to another pad.

Similar functionality is provided by gst_element_link_pads{_full}() however only
by pad name rather than by actual pads.

API: gst_pad_link_maybe_ghosting_full

https://bugzilla.gnome.org/show_bug.cgi?id=764176