Add mapper 498.

src/boards/asic_mmc1.h

@@ -32,6 +32,7 @@ void MMC1_syncCHR (int, int);
 void MMC1_syncMirror ();
 void FP_FASTAPASS(1) MMC1_cpuCycle(int);
 DECLFW (MMC1_writeReg);
+void MMC1_clear ();
 void MMC1_addExState ();
 void MMC1_restore (int);
 void MMC1_power ();