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.h

@@ -110,7 +110,7 @@ void FCEU_PutImageDummy(void);
 #endif
 
 extern uint8 Exit;
-extern uint8 pale;
+extern uint8 default_palette_selected;
 extern uint8 vsdip;
 
 #define JOY_A        0x01