Partial fix to #463, http://bugs.skysql.com/show_bug.cgi?id=463

log_manager.cc: fixed block buffer overflow. Queries are logged to trace log and long queries exceed the bufsize in length. Those were written beyond allocated memory areas.
mysql_client_server_protocol.h: added mysql_protocol_state_t to indicate whether MySQL protocol object is allocated, usable or freed. Freed means that memory allocations made by the protocol are freed. That is, command history etc.
mysql_backend.c: gw_backend_hangup and gw_error_backend_event used to call error handling function although session was already closing. Added check for session state.
mysql_client.c: route_by_statement lost some packets in case where query was sent in multiple packets.
mysql_common.c: gw_MySQL_get_next_packet failed in packet handling with route_by_statement. When multi-packet query was merged into one, packet type wasn't copied.
	protocol_archive_srv_command and mysql_protocol_done didn't have proper locking in place which lead to occasional crashes.

server/modules/include/mysql_client_server_protocol.h

@@ -102,6 +102,12 @@ typedef enum {
         MYSQL_IDLE
 } mysql_auth_state_t;
 
+typedef enum {
+        MYSQL_PROTOCOL_ALLOC,
+        MYSQL_PROTOCOL_ACTIVE,
+        MYSQL_PROTOCOL_DONE
+} mysql_protocol_state_t;
+
 
 /*
  * MySQL session specific data
@@ -270,6 +276,7 @@ typedef struct {
         server_command_t    protocol_command;             /*< session command list */
         server_command_t*   protocol_cmd_history;         /*< session command history */
         mysql_auth_state_t  protocol_auth_state;          /*< Authentication status */
+        mysql_protocol_state_t protocol_state;            /*< Protocol struct status */
         uint8_t             scramble[MYSQL_SCRAMBLE_LEN]; /*< server scramble,
         * created or received */
         uint32_t            server_capabilities;          /*< server capabilities,