Support multiple z80 speeds.

lib/emuctl/z80.bat

@@ -1,2 +1,18 @@
-rem Goto normal z80 speed
+rem Select z80 speed
-omsxctl set speed 100
+IFF 3 == %1
+	echo 'Select 3.51 Mhz'
+	omsxctl set speed 100
+	exit 0
+ENDIFF
+IFF 7 == %1
+	echo 'Select 7 Mhz'
+	omsxctl set speed 200
+	exit 0
+ENDIFF 
+IFF 11 == %1
+	echo 'Select 11 Mhz'
+	omsxctl set speed 333
+	exit 0
+ENDIFF
+echo 'Select openMSX Z80 emulation speed'
+echo 'Usage: z80 <3/7/11>'