X64 Crankshaft: Fix error in r6897.  Restore context register after KeyedCallIC.  Only non-trivial change is to lithium-codegen-x64.cc.Update copyright dates on all recently modified X64 platform files.  
Review URL: http://codereview.chromium.org/6592008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6952 ce2b1a6d-e550-0410-aec6-3dcde31c8c00