XFail TestLambdas.py on Windows after fixing some of the problems

1. Fixed semicolon placement in the lambda in the test itself.

2. Fixed lldbinline tests in general so that we don't attempt tests on platforms that don't use the given type of debug info. (For example, no DWO tests on Windows.) This fixes one of the two failures on Windows. (TestLambdas.py was the only inline test that wasn't XFailed or skipped on Windows.)

3. Set the error string in IRInterpreter::CanInterpret so that the caller doesn't print (null) instead of an explanation. I don't entirely understand the error, so feel free to suggest a better wording.

4. XFailed the test on Windows. The interpreter won't evaluate the lambda because the module has multiple function bodies. I don't exactly understand why that's a problem for the interpreter nor why the problem arises only on Windows.

Differential Revision: http://reviews.llvm.org/D19606

llvm-svn: 268573