Since m_option.h and options.h are extremely often included, a lot of
files have to be changed.
Moving path.c/h to options/ is a bit questionable, but since this is
mainly about access to config files (which are also handled in
options/), it's probably ok.
This will allow old filter to run libavfilter instead by calling
vf_lw_set_graph(), which turns the filter into a wrapper, using a given
libavfilter graph.
Later commits use that to automatically "reroute" a bunch of filters to
libavfilter. We want to get rid of the old MPlayer filter code, because
it's bad an unmaintained, but we still don't want to force everyone to
use vf_lavfi, so this solution will do for a while.
wm4