Fix MSVC: Doesn't have intrin0.h until 2017.

Also fixed a similar _MSC_VER guard that I realized was catching MinGW by accident.

c++/src/kj/filesystem-disk-win32.c++

@@ -298,7 +298,7 @@ protected:
   }
 };
 
-#if _MSC_VER < 1910
+#if _MSC_VER && _MSC_VER < 1910
 // TODO(msvc): MSVC 2015 can't initialize a constexpr's vtable correctly.
 const MmapDisposer mmapDisposer = MmapDisposer();
 #else

c++/src/kj/refcount.h

@@ -29,8 +29,12 @@
 #endif
 
 #if _MSC_VER
+#if _MSC_VER < 1910
+#include <intrin.h>
+#else
 #include <intrin0.h>
 #endif
+#endif
 
 namespace kj {