added slave_net_timeout

sql/mysqld.cc:
  slave_net_timeout
sql/slave.cc:
  slave_net_timeout
sql/slave.h:
  slave_net_timeout

sql/mysqld.cc

@@ -262,6 +262,7 @@ ulong keybuff_size,sortbuff_size,max_item_sort_length,table_cache_size,
       net_interactive_timeout, slow_launch_time = 2L,
       net_read_timeout,net_write_timeout,slave_open_temp_tables=0,
       open_files_limit=0, max_binlog_size;
+ulong slave_net_timeout;
 ulong thread_cache_size=0, binlog_cache_size=0, max_binlog_cache_size=0;
 volatile ulong cached_thread_count=0;
 
@@ -2740,6 +2741,8 @@ CHANGEABLE_VAR changeable_vars[] = {
       0, MALLOC_OVERHEAD, (long) ~0, MALLOC_OVERHEAD, IO_SIZE },
   { "record_buffer",           (long*) &my_default_record_cache_size,
       128*1024L, IO_SIZE*2+MALLOC_OVERHEAD, ~0L, MALLOC_OVERHEAD, IO_SIZE },
+  { "slave_net_timeout",        (long*) &slave_net_timeout, 
+      SLAVE_NET_TIMEOUT, 1, 65535, 0, 1 },
   { "slow_launch_time",        (long*) &slow_launch_time, 
       2L, 0L, ~0L, 0, 1 },
   { "sort_buffer",             (long*) &sortbuff_size,
@@ -2856,6 +2859,7 @@ struct show_var_st init_vars[]= {
   {"query_buffer_size",       (char*) &query_buff_size,		    SHOW_LONG},
   {"safe_show_database",      (char*) &opt_safe_show_db,            SHOW_BOOL},
   {"server_id",               (char*) &server_id,		    SHOW_LONG},
+  {"slave_net_timeout",       (char*) &slave_net_timeout,	    SHOW_LONG},
   {"skip_locking",            (char*) &my_disable_locking,          SHOW_MY_BOOL},
   {"skip_networking",         (char*) &opt_disable_networking,      SHOW_BOOL},
   {"skip_show_database",      (char*) &opt_skip_show_db,            SHOW_BOOL},

sql/slave.cc

@@ -678,6 +678,7 @@ static int init_slave_thread(THD* thd)
   thd->system_thread = thd->bootstrap = 1;
   thd->client_capabilities = 0;
   my_net_init(&thd->net, 0);
+  thd->net.timeout = slave_net_timeout;
   thd->max_packet_length=thd->net.max_packet;
   thd->master_access= ~0;
   thd->priv_user = 0;

sql/slave.h

 #ifndef SLAVE_H
 #define SLAVE_H
 
+#define SLAVE_NET_TIMEOUT  3600
+
+extern ulong slave_net_timeout;
+
 typedef struct st_master_info
 {
   char log_file_name[FN_REFLEN];