update and improve emulator

emulator/generate-and-compile.bat

@@ -0,0 +1,7 @@
+rem This is the procedure to generate the C code for the emulator backend
+rem from the instruction definitions in the parent directory,
+rem and compile it.
+
+luajit gendefs.lua
+gcc 8608emulator.c -shared -Ofast -o 8608emulator.dll
+pause