Fixed compiler warnings from gcc 4.0.2:

- Added empty constructors and virtual destructors to many classes and structs
- Removed some usage of the offsetof() macro to instead use C++ class pointers


configure.in:
  Added comment
ndb/include/ndbapi/NdbDictionary.hpp:
  Fixed compiler warnings from gcc 4.0.2
sql/field.cc:
  Fixed compiler warnings from gcc 4.0.2
sql/handler.h:
  Fixed compiler warnings from gcc 4.0.2
sql/item.h:
  Fixed compiler warnings from gcc 4.0.2
sql/item_cmpfunc.h:
  Fixed compiler warnings from gcc 4.0.2
sql/log_event.h:
  Fixed compiler warnings from gcc 4.0.2
sql/mysql_priv.h:
  Fixed compiler warnings from gcc 4.0.2
  For find_table_in_list I fixed it to use proper C++ class pointers instead of C style pointers
sql/opt_range.cc:
  Fixed compiler warnings from gcc 4.0.2
sql/parse_file.h:
  Fixed compiler warnings from gcc 4.0.2
sql/sp_rcontext.h:
  Fixed compiler warnings from gcc 4.0.2
sql/spatial.h:
  Fixed compiler warnings from gcc 4.0.2
sql/sql_base.cc:
  Fixed compiler warnings from gcc 4.0.2
sql/sql_cache.h:
  Fixed compiler warnings from gcc 4.0.2
sql/sql_class.h:
  Fixed compiler warnings from gcc 4.0.2
sql/sql_parse.cc:
  Fixed compiler warnings from gcc 4.0.2
  (Not pretty, but seams to work...)
sql/sql_select.h:
  Fixed compiler warnings from gcc 4.0.2
sql/sql_update.cc:
  Fixed compiler warnings from gcc 4.0.2
sql/table.h:
  Fixed compiler warnings from gcc 4.0.2
sql/tztime.cc:
  Fixed compiler warnings from gcc 4.0.2
sql/tztime.h:
  Fixed compiler warnings from gcc 4.0.2

sql/sql_base.cc

@@ -687,11 +687,11 @@ void close_temporary_tables(THD *thd)
 */
 
 TABLE_LIST *find_table_in_list(TABLE_LIST *table,
-                               uint offset,
+                               st_table_list *TABLE_LIST::*link,
                                const char *db_name,
                                const char *table_name)
 {
-  for (; table; table= *(TABLE_LIST **) ((char*) table + offset))
+  for (; table; table= table->*link )
   {
     if ((table->table == 0 || table->table->s->tmp_table == NO_TMP_TABLE) &&
         strcmp(table->db, db_name) == 0 &&