proper mbc type. use double-speed mode on gbc.

Makefile

 ROMU := $(GBDK_HOME)/bin/romusage
 GB_EMU := gearboy
 
-LCCFLAGS := -Wa-l -Wl-m -Wp-MMD # -Wf--opt-code-speed
+LCCFLAGS := -Wa-l -Wl-m -Wp-MMD -Wf--opt-code-speed
 LCCFLAGS += -I$(BUILD_DIR)/$(DATA_DIR)
-LCCFLAGS += -Wm"-yn Duality" -Wm-yt0x1A -Wm-yoA -Wm-ya16 -Wm-yc
+LCCFLAGS += -Wm"-yn Duality" -Wm-yt0x1B -Wm-yoA -Wm-ya16 -Wm-yc
 LCCFLAGS += -autobank -Wb-ext=.rel -Wb-v -Wf-bo255
 
 EMUFLAGS := $(BIN)

src/main.c

 }
 
 void main(void) NONBANKED {
+    // "cheat" and enable double-speed CPU mode on GBC
+    if (_cpu == CGB_TYPE) {
+        cpu_fast();
+    }
+
     spr_init();
     snd_init();