Adding test-case for llvm.org/pr15936 (known failure with GCC 4.6/4.7)
- verify that backtraces for stacks that include functions which contain 
  illegal instructions are correct, and that variables in said functions can be
  printed.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@181442 91177308-0d34-0410-b5e6-96231b3b80d8