Update git submodules
- Update extensions/Math from branch 'REL1_39' to 8037a7ad39d94bcb9ac43e2a7db7ad2af98fbe45
- Localisation updates from https://translatewiki.net.
Change-Id: I619e5bc5bb6e40c82691f462ddfe1d7a625fe6ce
- Localisation updates from https://translatewiki.net.