Update MIN protocol to permit frame sizes up to 255 bytes

[kentindell]

Should also stretch stuff byte for headers to 0xaa 0xaa 0xaa 0xaa so that a stuff byte is worst-case at most every three bytes, not two. This will reduce the size of the frame buffer that needs to be allocated.

Configure the embedded code to allow for a smaller buffer such that larger MIN frames are rejected. This will support smaller devices that cannot afford to allocate a large buffer and where the application doesn't need large frames.