atsign-doc forces functions to be imported/extended

[timholy]

This works:

module Doc

@doc "read" ->
Base.read(filename) = 1

end

but if you take away the Base. (to require folks to call read as Doc.read) then you get

julia> using Doc
ERROR: LoadError: error in method definition: function Base.read must be explicitly imported to be extended
 in include at ./boot.jl:254
 in include_from_node1 at ./loading.jl:133
 in reload_path at ./loading.jl:157
 in _require at ./loading.jl:69
 in require at ./loading.jl:52
while loading /tmp/Doc.jl, in expression starting on line 3

Naturally, a function that does not have a name-conflict with Base does not have this problem.

[MichaelHatherly]

@one-more-minute I've got a possible fix for this. Unless you've been working on this already I'll PR it in a bit.

[MikeInnes]

Sure, would be great to see what you got.