Tweaks to r19987:

Tweaks to r19987:
* Don't add an 'id' attribute for custom toolbar buttons where the
  custom array doesn't include an id, for compatibility with
  existing settings.
* Fix corrupted, but previously also incorrect, encoding on regex
  for currencies in sortable table setup. Using \u escape sequences
  for pound and euro; possibly other symbols need to be added?
* Bump $wgStyleVersion