build lua dll module in mingw/msys

1. install mingw/msys , base_mingw,base_msys,g++
2. postinstall msys

3. download & build lua 5.1.5
    make mingw
4. write a dll4lua.c   
    gcc  -O2  -c  -o dll4lua.o  dll4lua.c
    gcc  -O    -shared -o dll4lua.dll  dll4lua.o -llua