Change codec so it does not crashed on func

Currently Bert crashes when faced with an Erlang fun (http://erlang.org/doc/apps/erts/erl_ext_dist.html#id90022). I am not sure what the appropriate decoding for a fun is, but mostly I find it useful if I can actually read the file (I don't think it makes sense to try and run a fun on Python).

This code just adds enough to skip the NEW_FUN_EXT terms in a Bert blob.