Update VE core submodule to master (b6b80c2)

New changes:
1dceca8 Fix shadow position in standalone toolbar
8f3f1b1 Localisation updates from https://translatewiki.net.
1a52e71 Localisation updates from https://translatewiki.net.
f53e80a Localisation updates from https://translatewiki.net.
4395f26 InputLabelWidget -> LabelWidget
d7ecba8 Localisation updates from https://translatewiki.net.
aa79a89 Fix SurfaceWidget documentation
c6ba29c Fix layout of keyboard shortcuts page
d871d48 Allow getAnnotationsFromOffset to ignore close elements,
627ced3 Fix ce#getOffset when cursor is to the left of an annotation.
b6b80c2 Dialog: Fix inline comment to use /* instead of /**.

Change-Id: I78a3d992660040281790d303b447de8cd7ee9acc