Update git submodules
- Update extensions/Gadgets from branch 'REL1_39' to fb257e339eba15e9276debf876be09553b5e5a8a
- Localisation updates from https://translatewiki.net.
Change-Id: I4250044164bdb54e702b9322841e4233979e7a4e
- Localisation updates from https://translatewiki.net.