Update git submodules
- Update extensions/Gadgets from branch 'REL1_39' to 13d5d5e78132c3021ccb2f448752f6b9a92d05cd
- Localisation updates from https://translatewiki.net.
Change-Id: If660738c9913de6a7de0e3eca9e9bc56af8d4656
- Localisation updates from https://translatewiki.net.