MacOSKeychainAPIChecker:

Report errors earlier: on checkDeadSymbols() and clear the state after the symbol we are tracking goes out of scope. 

Also, perform lazy error checking. Instead of forcing the paths to be split depending one the return value of the allocator, make the return symbol depend on the allocated data symbol, which prolongs its life span to the time when the allocated data symbol becomes dead.

llvm-svn: 137523