[analyzer] MIGChecker: Take advantage of the mig_server_routine annotation.
r354530 has added a new function/block/message attribute "mig_server_routine"
that attracts compiler's attention to functions that need to follow the MIG
server routine convention with respect to deallocating out-of-line data that
was passed to them as an argument.
Teach the checker to identify MIG routines by looking at this attribute,
rather than by making heuristic-based guesses.
rdar://problem/
35380337
Differential Revision: https://reviews.llvm.org/58366
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@354638
91177308-0d34-0410-b5e6-
96231b3b80d8