Update VE core submodule to master (dc8cf63)

New changes:
38fc5bb Replace native range rectangle hacks with RangeFix library
4713b8e Disable cell editing when a context is opened
1113a13 AUTHORS.txt: Re-update for late 2014
37af5c4 Prevent clicks on focusable nodes in tables
2152877 Localisation updates from https://translatewiki.net.
b766ecc Update OOjs UI to v0.1.0-pre (eee616d664)
20cb077 Follow-up Ifb7ffb1: Update demo.js for breaking OOUI change
6760cdd Localisation updates from https://translatewiki.net.
555c6ea Set insertion annotations when typing over cell contents
819ad6b Fix width of demo page dropdown
9f4705c Catch backwards selection error in Firefox
ac8a4e8 Add missing focus call to pasteTarget
b034657 Add support for non-table nodes in tables (e.g. aliens)
25aef0c Fixes to onDocumentDrop
622957f Add support for dropping text/html from external sources

Change-Id: Ic704b95c1dc91a1ae74f9a60101cb949b34c9e0d