Fix  #20
Fix  #20

See #20 for context:

> allows the procedure to be stored in a variable and called correctly (even with default parameters).
> As said by Araq on IRC:
>> 'procvar' doesn't do much [...] it's just another check for semantic checking. codegen is not affected.
tmm1/nim-by-example,zhjh1209/nim-by-example.github.io,flaviut/nim-by-example,tmm1/nim-by-example,flaviut/nim-by-example,tmm1/nim-by-example,flaviut/nim-by-example,flaviut/nim-by-example,zhjh1209/nim-by-example.github.io,tmm1/nim-by-example