[attributes] Add a family of OS_CONSUMED, OS_RETURNS and OS_RETURNS_RETAINED attributes

The addition adds three attributes for communicating ownership,
analogous to existing NS_ and CF_ attributes.
The attributes are meant to be used for communicating ownership of all
objects in XNU (Darwin kernel) and all of the kernel modules.
The ownership model there is very similar, but still different from the
Foundation model, so we think that introducing a new family of
attributes is appropriate.

The addition required a sizeable refactoring of the existing code for
CF_ and NS_ ownership attributes, due to tight coupling and the fact
that differentiating between the types was previously done using a
boolean.

Differential Revision: https://reviews.llvm.org/D54912

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@347947 91177308-0d34-0410-b5e6-96231b3b80d8

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