This patch fixes a problem where a CompilerInvocation
with no arguments would set the LangaugeOpts etc. up for
the deprecated-integrated-repl, including setting the
module name etc. Now this only happens if you explicitly
invoke swift -frontend -repl.
Updated testcases that care, and added a new testcase to
ensure that an error is properly generated.
<rdar://problem/17918172>
Swift SVN r21537