[perl6/specs] abb19a: Add "extension"

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/perl6/specs
  Commit: abb19a588af2797b63016e5e21f3c98df24843bb
      
https://github.com/perl6/specs/commit/abb19a588af2797b63016e5e21f3c98df24843bb
  Author: Elizabeth Mattijsen <l...@dijkmat.nl>
  Date:   2014-09-23 (Tue, 23 Sep 2014)

  Changed paths:
    M S16-io.pod

  Log Message:
  -----------
  Add "extension"