Add opelcn to ltrelre to iset.mm
Add opelcn to ltrelre to iset.mm

This is the theorems opelcn , opelreal , elreal , elreal2 , 0ncn ,
and ltrelre . They are copy-pasted from set.mm and the only change
is to remove discouraged tags.

metamath/set.mm,metamath/set.mm,metamath/set.mm