Extend the Stmt AST to make it easier to look through label, default,
and case statements. Use this to make the logic in the CFG builder more
robust at finding the actual statements within a compound statement,
even when there are many layers of labels obscuring it.

Also extend the test cases for a large chunk of PR10063. Still more work
to do here though.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@139437 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed