Improves macro expansion stacktraces, closes #2211
Improves macro expansion stacktraces, closes #2211

We make sure the paths in stacktraces are relatives
and properly point which macros are being expanded.

kimshrier/elixir,pedrosnk/elixir,ggcampinho/elixir,gfvcastro/elixir,ggcampinho/elixir,elixir-lang/elixir,kelvinst/elixir,michalmuskala/elixir,pedrosnk/elixir,beedub/elixir,kimshrier/elixir,joshprice/elixir,antipax/elixir,lexmag/elixir,antipax/elixir,beedub/elixir,kelvinst/elixir,gfvcastro/elixir,lexmag/elixir