[analyzer] Suppress null reports from defensive checks in function-like macros.

We already do this for case splits introduced as a result of defensive null
checks in functions and methods, so do the same for function-like macros.

rdar://problem/19640441

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@259222 91177308-0d34-0410-b5e6-96231b3b80d8