Update VE core submodule to master (d1f5386)

New changes:
2909ff9 Update OOjs UI to v0.1.0-pre (eba79af989)
1737a76 Add .focus() to SurfaceWidget
6fc4026 Code style typos
d1f5386 Update OOjs UI to v0.1.0-pre (8197f2cd2e)

Change-Id: Ia8edc2319ed0a4578652fb7e5b257061edd0a7c0
Merge "Update VE core submodule to master (d1f5386)"