Added __faststorefence() MSVC intrinsic (required e.g. by sqlite3).

lib/libtcc1.c

@@ -631,3 +631,11 @@ long long __fixxfdi (long double a1)
 const float __mzerosf = -0.0;
 const double __mzerodf = -0.0;
 #endif
+
+#if defined _WIN64
+/* MSVC x64 intrinsic */
+void __faststorefence(void)
+{
+    __asm__("lock; orl $0,(%rsp)");
+}
+#endif