[AntiDepBreaker] Revert r299124 and add a test.

Summary:
AntiDepBreaker intends to add all live-outs, including the implicit
CSRs, in StartBlock. r299124 was done without understanding that
intention.

Now with the live-ins propagated correctly (D32464), we can revert this change.

Reviewers: MatzeB, qcolombet

Subscribers: nemanjai, llvm-commits

Differential Revision: https://reviews.llvm.org/D33697

llvm-svn: 304251