Add UBSan blacklist for <__tree> and <__hash_table>

We all know <__tree> and <__hash_table> have plenty of UB that UBSan faithfully
finds. I am working on fixing this. However the noisy output from these failures
prevent automatically detecting regressions elsewhere.

This patch adds a blacklist file for these failures so I can later set up a
UBSAN buildbot.

llvm-svn: 273104