Add case for MSVC

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>

library/common.h

diff --git a/library/common.h b/library/common.h
index 7652e56..fe4d213 100644
--- a/library/common.h
+++ b/library/common.h
@@ -330,8 +330,13 @@
 #endif
 #endif
 #if !defined(MBEDTLS_ASSUME)
+#if defined(_MSC_VER)
+/* Supported by MSVC since VS 2005 */
+#define MBEDTLS_ASSUME(x)       __assume(x)
+#else
 #define MBEDTLS_ASSUME(x)       do { } while (0)
 #endif
+#endif
 
 #if defined(__GNUC__) && !defined(__ARMCC_VERSION) && !defined(__clang__) \
     && !defined(__llvm__) && !defined(__INTEL_COMPILER)