Update VE core submodule to master (c231b71)

New changes:
c9f1027 Remove broken ve.isMsie() function
6571da1 Fix case on language annotation CSS class
c231b71 Fix case in all annotation classes

Local changes:
Fix case in all annotation classes

Change-Id: Iba2596cde52d8f8be27e0257893ef8ec77798ae8