Authentication protocol can be changed, a new raw
packet is introduced, which includes only the "encrypted"
data for the auth plugin, sent after change protocol (0xFE)
is sent to the client.
structure and where they load themselves.
0xFE packets (method switch) needs to be done, additional
wire-level packet to be created to be parsed and the packet
doesn't fit the PACKET_OK structure anymore.
Move the authentication routines, the native ones, to
separate file and encapsulate them in a plugin.
Depending on the server version and what the server
requests (or doesn't in old versions) load the authentication
plugin to handle it.
Currently only the 4.1+ authentication is supported. More to come
