Fixed warning : 'va_copy' : macro redefinition
MSVC 2013 has got va_copy
Compare
http://msdn.microsoft.com/en-us/library/kb57fad8(v=vs.110).aspx
and
http://msdn.microsoft.com/en-us/library/kb57fad8.aspx.

Change-Id: If0937c76e8d250cde4b343844f3d35c980bf0921