Updated the Galician translation of the “Descent Into Darkness” map.
Merge branch 'gl' of https://github.com/Gallaecio/wesnoth-old
Optipng run on gl did--overlay.png

Overall statistics (only for files with a smaller recompressed size):
  Original size: 130 KiB on 1 files
 Optimized size: 121 KiB
   Total saving: 8 KiB = 6% decrease
l10n-track update