Support new Dbgi chunk introduced in Erlang/OTP 20

[erszcz]

This breaks CI builds on 20.0. See erlang/otp#1367.

[erszcz]

As of commit d037bd5 the status is as follows.

Erlang 19.2:

2> s(fun docsh_erl:h/1).

docsh_erl:h/1

-spec h(fun() | module()) -> ok.

ok
3> h(fun docsh_erl:h/1).

docsh_erl:h/1

-spec h(fun() | module()) -> ok.

When invoked with a module as an argument like h(lists),
then look up the module documentation.
When invoked with a fun as the argument like h(fun lists:keyfind/3),
then equivalent to h(M, F, A) with the the fun's deduced
{M :: module(), F :: name(), A :: arity()}.

ok
4>

Erlang 20.2:

3> s(fun docsh_erl:h/1).
Abstract code for docsh_erl is not available.

docsh: no spec for docsh_erl:h/1

ok
4> h(fun docsh_erl:h/1).

docsh_erl:h/1

When invoked with a module as an argument like h(lists),
then look up the module documentation.
When invoked with a fun as the argument like h(fun lists:keyfind/3),
then equivalent to h(M, F, A) with the the fun's deduced
{M :: module(), F :: name(), A :: arity()}.

ok
5>