Update git submodules
- Update extensions/Gadgets from branch 'REL1_39' to 1b2f13f72e088a13b65d81de59f3af6fd86f8485
- Localisation updates from https://translatewiki.net.
Change-Id: I86eee3791a9ccf5c9972d4cc5129c753da32ea38
- Localisation updates from https://translatewiki.net.