defcodec- does not create private Vars

[akahl-owl]

The Vars created with defcodec- are not private and remain accessible from outside the namespaces they are defined in.

user> (require '[gloss.core :refer :all])
nil
user> (defcodec- foo :byte)
#'user/foo
user> (meta #'foo)
{:line 78, :column 6, :file "*cider-repl localhost*", :name foo, :ns #namespace[user]}

I will create pull request to fix this issue.