add bitcode reader support for blockaddress.  We can now fully
round trip blockaddress through .ll and .bc files, so add a testcase.

There are still a bunch of places in the optimizer and other places
that need to be updated to work with these constructs, but at least
the basics are in now.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85377 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed