Don't create an extra user interface object when in interactive mode.
Simplify.
In the case where we run cling -verify we must check whether it issued errors and
return unhappiness as an exit code from the process. This is helpful for cling's
test suite, because this gives the suite chance to understand that something
went wrong.

The implementation is a bit hackish since the implementation of the
VerifyDiagnosticsConsumer requires EndSourceFile call to perform all necessary
checks. This means that we need to force it before Interpreter's dtor has done
it so that we still could have chance to set the return result of main. Then
we need to call artificially BeginSourceFile because the interpreter expects
balanced BeginSourceFile/EndSourceFils calls.
We check whether there is terminal attached and if not (as the case of the testsuite)
we don't need to answer the warning.
Add an XFAIL-ing test, as TODO for Baozeng.
Remove the expected error. We don't expect error there. The declared function
has an address, which could be evaluated.
Make sure that the value is valid.a
Call exit. This will do the extra sanity checks.
Return result of the process should be if there were diagnostics issued, that
weren't recovered.
Indents.
Already implemented, remove the fixme.
Merge branch 'master' of https://root.cern.ch/git/root