Overriding numbered members is not intuitive.
Merging {1} and {2} should return {1,2} not {2}.

Coalesce some event subscriptions

See merge request muhq/vis-lspc!60

Change vis_sel_to_pos to vis internals or to count lines itself

Closes #38

See merge request muhq/vis-lspc!58

At least in lua-cjson, null is sometimes returned as a (light) userdata
value. This resulted in ugly errors.