fixed compilation with Visual Studio 2005

lib/decompress/zstd_decompress.c

@@ -77,6 +77,7 @@
 #  include <intrin.h>                    /* For Visual 2005 */
 #  pragma warning(disable : 4127)        /* disable: C4127: conditional expression is constant */
 #  pragma warning(disable : 4324)        /* disable: C4324: padded structure */
+#  pragma warning(disable : 4100)        /* disable: C4100: unreferenced formal parameter */
 #else
 #  ifdef __GNUC__
 #    define FORCE_INLINE static inline __attribute__((always_inline))