[analyzer] Add the pointer escaped callback.

Instead of using several callbacks to identify the pointer escape event,
checkers now can register for the checkPointerEscape.

Converted the Malloc checker to use the new callback.
SimpleStreamChecker will be converted next.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@170625 91177308-0d34-0410-b5e6-96231b3b80d8
16 files changed