g-ir-scanner includes section docs as class/interface docs if the section name is equal to the lowercase type name.
Since all the documentation is in section blocks, rename them to match the type names.
https://bugzilla.gnome.org/show_bug.cgi?id=727776
It might be needed in some cases (for example when decoding prores files) and
it is the way it is done with playbin now. Also deinterlace now properly supports
passtrough mode.
