[analyzer] Malloc: A pointer might escape through CFContainers APIs,

[analyzer] Malloc: A pointer might escape through CFContainers APIs,
funopen, setvbuf.

Teach the checker and the engine about these APIs to resolve malloc
false positives. As I am adding more of these APIs, it is clear that all
this should be factored out into a separate callback (for example,
region escapes). Malloc, KeyChainAPI and RetainRelease checkers could
all use it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@151737 91177308-0d34-0410-b5e6-96231b3b80d8