[AST] Use data-recursion when building ParentMap, avoid stack overflow.

The following crashes on my system before this patch, but not after:

  void foo(int i) {
    switch (i) {
      case 1:
      case 2:
      ... 100000 cases ...
        ;
    }
  }

  clang-query -c="match stmt(hasAncestor(stmt()))" deep.c

I'm not sure it's actually a sane testcase to run though, it's pretty slow :-)

Differential Revision: https://reviews.llvm.org/D88222