Eliminate a user manual warning
authorSimon Peyton Jones <simonpj@microsoft.com>
Mon, 27 Mar 2017 09:09:37 +0000 (10:09 +0100)
committerSimon Peyton Jones <simonpj@microsoft.com>
Mon, 27 Mar 2017 13:40:55 +0000 (14:40 +0100)
commitaf33073c77e409d594e61609b3fba7070766cb75
treeeda8087185bd24b8ffd9e74e1d0e2997baee849e
parent1e06d8b8f2aea0a06d40618c296a034f3e408ae2
Eliminate a user manual warning

I was getting
  docs/users_guide/glasgow_exts.rst:12783:
     WARNING: Title underline too short.

  ``COLUMN`` pragma
  ---------------

So I lengthened the row of hyphens.
docs/users_guide/glasgow_exts.rst