Update git submodules
- Update extensions/Gadgets from branch 'REL1_39' to 7436453301f94d1d47ea7118ddac3d64def5659b
- Localisation updates from https://translatewiki.net.
Change-Id: I395d1630feec893e25413e6f089f585412ab970a
- Localisation updates from https://translatewiki.net.