Specify checksums properly for llgs test suite packets.

Summary: These checksums are ignored by llgs but some implementations require them to be specified properly.

Test Plan: Re-run llgs tests with the checksums and make sure we don't break anything.

Reviewers: tfiala, clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D6254
Use unique_ptr to handle ownership of TreePatterns in CodeGenDAGPatterns::PatternFragments

We might be able to use unique_ptr to handle ownership of the
TreePatternNodes too - looking into that next.