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/gfxinit.cpp

@@ -304,6 +304,9 @@ static bool SwitchNewGRFBlitter()
 #endif
 		{ "8bpp-optimized",  2,  8,  8,  8,  8 },
 		{ "32bpp-optimized", 0,  8, 32,  8, 32 },
+#ifdef WITH_SSE
+		{ "32bpp-sse2-anim", 1,  8, 32,  8, 32 },
+#endif
 		{ "32bpp-anim",      1,  8, 32,  8, 32 },
 	};