clang-cl: Add a FIXME for bumping the default msc version.

llvm-svn: 264216
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index b18ddd4..7d69756 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3259,6 +3259,7 @@
     if (Major || Minor || Micro)
       return VersionTuple(Major, Minor, Micro);
 
+    // FIXME: Consider bumping this to 19 (MSVC2015) soon.
     return VersionTuple(18);
   }
   return VersionTuple();