Report unexpected output in test output

LitTestCommand has a set of descriptions for test result codes, and
ends up throwing an exception if an unexpected result is somehow
produced by a test run.  This happens with the LLDB tests.

Differential Revision: http://reviews.llvm.org/D4775


git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@214767 91177308-0d34-0410-b5e6-96231b3b80d8