Add support for 512 palette, new deepmhasis method

- Increase palette table from 256 to 1024. the 1st 256 colors are used
  by FCEUmm internally and for compatibility (PS2/PSP will use the old
  emphasis located in this area). New 512 colors with emphasis will be
  read from offset 256 of this palette table.
- Support loading of 512 palette, this will still use the same nes.pal
  filename.

src/fceu.c

@@ -224,7 +224,7 @@ void ResetGameLoaded(void)
 	MMC5Hack = 0;
 	PEC586Hack = 0;
 	PAL &= 1;
-	pale = 0;
+	default_palette_selected = 0;
 }
 
 int UNIFLoad(const char *name, FCEUFILE *fp);