ObjectiveC: Don't warn when method implemented in
category is declared in category's primary
class's super class. Because the super class is
expected to implemented the method. // rdar://15580969


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@196531 91177308-0d34-0410-b5e6-96231b3b80d8