libvlc: refactor sfilter enabling/disabling

libvlc: refactor sfilter enabling/disabling

Refactor sfilter enabling and disabling. One glitch stays present:
A user needs to call libvlc_{logo,marq,adjust}_int{ p_mi, libvlc_{logo,marq,adjust}_Enable, twice initially. Once before setting options to get module to load and second after setting options. After this Enabling/Disabling works as expected.
NOTE: when changing an option one MUST call
libvlc_{logo,marq,adjust}_int{ p_mi, libvlc_{logo,marq,adjust}_Enable, again.

The patch removes the dependency on the deprecated function vlc_object_find_name()