[asan] introduce __asan_load_cxx_array_cookie: check that the array cookie address is properly poisoned and return the cookie value. If not, return 0 to avoid infinite loop of DTORs (in case of use-after-free). Calls to this function will be inserted by clang (separate change)

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@216692 91177308-0d34-0410-b5e6-96231b3b80d8