win: Add an explicit intrin.h include to work around a clang-cl bug.

src/shared/platform/win/nacl_secure_random.c

Index: src/shared/platform/win/nacl_secure_random.c
diff --git a/src/shared/platform/win/nacl_secure_random.c b/src/shared/platform/win/nacl_secure_random.c
index f549441bab6d784d74a7fa1063ed5a2012cb8fab..b73766fccf702e3f0891e4dac1477fb55e9256fc 100644
--- a/src/shared/platform/win/nacl_secure_random.c
+++ b/src/shared/platform/win/nacl_secure_random.c
@@ -9,6 +9,14 @@
  */
 #include <windows.h>
 
+/* Work around a clang-cl bug: SecureZeroMemory() below uses __stosb() but
+ * windows.h only declares that intrinsic and then uses `#pragma intrinsic` for
+ * it.  clang-cl doesn't implement `#pragma intrinsic` yet; it instead defines
+ * the function as an always-inline symbol in its intrin.h.
+ * TODO(thakis): Remove this once http://llvm.org/PR19898 is fixed.
+ */
+#include <intrin.h>
+
 /*
  * #define needed to link in RtlGenRandom(), a.k.a. SystemFunction036. See
  * the "Community Additions" comment on MSDN here: