after Monty's review.
- Item_param was rewritten.
- it turns out that we can't convert string data to character set of
connection on the fly, because they first should be written to the binary
log.
To support efficient conversion we need to rewrite prepared statements
binlogging code first.
Extended max_allowed_packet for clients to 1G
Fixed bug in sending compressed rows >= 16M
Fix bug in skiping too long packets from clients.
Added checking of wrong command number sent by client.
