Fixed many compiler warnings

Fixed bugs in group_concat with ORDER BY and DISTINCT (Bugs #2695, #3381 and #3319)
Fixed crash when doing rollback in slave and the io thread catched up with the sql thread
Set locked_in_memory properly

sql/sql_prepare.cc

@@ -1121,9 +1121,10 @@ static void reset_stmt_for_execute(Prepared_statement *stmt)
 void mysql_stmt_execute(THD *thd, char *packet, uint packet_length)
 {
   ulong stmt_id= uint4korr(packet);
+#ifndef EMBEDDED_LIBRARY
   uchar *packet_end= (uchar *) packet + packet_length - 1;
+#endif
   Prepared_statement *stmt;
-
   DBUG_ENTER("mysql_stmt_execute");
 
   packet+= 9;                               /* stmt_id + 5 bytes of flags */