[PATCH] Fixing a struct layout bug with bitfields before virtual base

[Yunzhong Gao]

  I talked with Warren over email. Warren does not have objections to the patch, although he did mention that
  he is working on a complete rewrite of CGRecordLayoutBuilder, which will not integrate with this patch. My
  plan is to commit this patch anyway and hence add the test case in the mean time.

http://llvm-reviews.chandlerc.com/D2560