clang-cl: add the /c, /W0 and /W1 options

This adds a few more clang-cl options. It also exposes two core clang
options to the clang-cl mode: we need to be able to claim --driver_mode
so it doesn't show up as unused in cl mode, and we need -### for tests.

Differential Revision: http://llvm-reviews.chandlerc.com/D1232

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187527 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Driver.cpp b/lib/Driver/Driver.cpp
index 34594e6..4f9cd3e 100644
--- a/lib/Driver/Driver.cpp
+++ b/lib/Driver/Driver.cpp
@@ -1883,9 +1883,9 @@
   unsigned ExcludedFlagsBitmask = 0;
 
   if (Mode == CLMode) {
-    // Only allow CL options.
-    // FIXME: Also allow "core" Clang options.
-    IncludedFlagsBitmask = options::CLOption;
+    // Include CL and Core options.
+    IncludedFlagsBitmask |= options::CLOption;
+    IncludedFlagsBitmask |= options::CoreOption;
   } else {
     ExcludedFlagsBitmask |= options::CLOption;
   }