Add support for MSVC

Tested with MSVC 8 32 and 64 bits.

include/msvc_compat/strings.h

@@ -0,0 +1,23 @@
+#ifndef strings_h
+#define strings_h
+
+/* MSVC doesn't define ffs/ffsl. This dummy strings.h header is provided
+ * for both */
+#include <intrin.h>
+#pragma intrinsic(_BitScanForward)
+static __forceinline int ffsl(long x)
+{
+	unsigned long i;
+
+	if (_BitScanForward(&i, x))
+		return (i + 1);
+	return (0);
+}
+
+static __forceinline int ffs(int x)
+{
+
+	return (ffsl(x));
+}
+
+#endif