Implement a 32bpp SSE2 palette animator. This is ~4x faster than 32bpp-anim's.

Create a new blitter mode: 32bpp-sse2-anim, which is 32bpp-anim + this.
32bpp-sse2-anim is now used by default where 32bpp-anim would have been.
Also use this with the 32bpp-sse4-anim blitter mode.

Fix memory leak in current 32bpp animated blitters.

src/stdafx.h

@@ -542,4 +542,12 @@ static inline void free(const void *ptr)
 	#define PREFETCH_NTA(address)
 #endif
 
+#ifdef __GNUC__
+#define likely(x)       __builtin_expect(!!(x), 1)
+#define unlikely(x)     __builtin_expect(!!(x), 0)
+#else
+#define likely(x)       (x)
+#define unlikely(x)     (x)
+#endif
+
 #endif /* STDAFX_H */