add menu_cfg variable(0x8308)
update README doc.
write command now can use --bytes parameter limits the number of bytes to be written
fix bug in if_func; googlecode [issue 186](https://code.google.com/p/grub4dos-chenall/issues/detail?id=186)
Merge branch 'master' into 0.4.6a

* master:
  fix bug in if_func; googlecode [issue 186](https://code.google.com/p/grub4dos-chenall/issues/detail?id=186)
  update README doc.
  add menu_cfg variable(0x8308)