* Attempt to un-break gdb buildbot by emitting a lexical block end only
  when we actually end a lexical block.
* Added new test for line table / block cleanup.
* Follow-up to r177819 / rdar://problem/13115369

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@178490 91177308-0d34-0410-b5e6-96231b3b80d8