Update VE core submodule to master (5aa55c5)

New changes:
f8a0e73 Followup 7e39f497: call parent method in DialogTool so disabling works
185a00f Fix typo in ve.dm.Scalable
63390ab Update OOjs UI to v0.1.0-pre (eca1fc20e7)
1f636cf Detect document focus properly and allow null selection in model
82ad081 Event sequencer cleanup
1b6a622 Create ve#contains
07132bc Prevent pasteTarget selection while already selected
32b7f47 Make the DOM hash ignore text node splitting
5243788 Revert "Make the DOM hash ignore text node splitting"
5aa55c5 Re-apply "Make the DOM hash ignore text node splitting"

Change-Id: I8c4ab05a0ff206fdca470c42008768626449e2bc