KeychainAPI checker: Add basic diagnostics. Track MemoryRegion istead of SymbolicRef since the address might not be a symbolic value in some cases, for example in fooOnlyFree() test.

llvm-svn: 136851

[analyzer] rename all experimental checker packages to have 'experimental' be the common root package.

llvm-svn: 136835

KeychainAPI checker: only check the paths on which the allocator function returned noErr. (+ minor cleanup)

llvm-svn: 136694

Add a skeleton for the Keychain Services API Checker. Register it as OSX experimental for now. Note, the checker still does not handle tracking of escaped values, taking into account the return value of the allocator functions, nor the actual bug reporting.. 

llvm-svn: 136659