Option to not use the Miknet protocol

These commits introduce flags to miknodes, that can be used to modify the behavior of the miknodes. One flag in particular has also been added, MIK_FLAG_NOPROTO, which, when set, makes a miknode send and receive raw data instead of using the Miknet protocol.

Example:

```c
miknode_t node = { 0 };

miknode(&node, MIK_IPV4, 7000, 20);

// set "no proto" mode
miknode_set_flags(&node, MIK_FLAG_NOPROTO);

// ...
```