results: make engines of results set
results: make engines of results set

Previously, if a same result was returned from the
same engine, the name of the engine would be added
more than once. To eliminate engine name duplication
engine list was changed to set.

asciimoo/searx,asciimoo/searx,jcherqui/searx,misnyo/searx,dalf/searx,dalf/searx,misnyo/searx,jcherqui/searx,jcherqui/searx,dalf/searx,misnyo/searx,misnyo/searx,jcherqui/searx,dalf/searx,asciimoo/searx,asciimoo/searx