Update VE core submodule to master (4d919d2)

Implement new language platform functions.

Also remove unused MWLanguageSearchDialog and MWLanguageSearchWidget.

New changes:
4d919d2 [BREAKING CHANGE] Move language functions to the platform

Change-Id: I54c0a8e5816a3c81851f95f1d3062a6091a9f4a3