clang-cl: Parse the /d2Zi+ flag (PR18728)

This is an undocumented, but reportedly widely used flag.
We don't support it, but should be able to parse it.

llvm-svn: 201588
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index 4b5b603..78a64f5 100644
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -159,6 +159,7 @@
 // RUN:     /arch:sse2 \
 // RUN:     /clr:pure \
 // RUN:     /docname \
+// RUN:     /d2Zi+ \
 // RUN:     /EHsc \
 // RUN:     /EP \
 // RUN:     /F \