Added detection of memory overwrite with multi_malloc

This patch also fixes some bugs detected by valgrind after this
patch:

- Not enough copy_func elements was allocated by Create_tmp_table() which
  causes an memory overwrite in Create_tmp_table::add_fields()
  I added an ASSERT() to be able to detect this also without valgrind.
  The bug was that TMP_TABLE_PARAM::copy_fields was not correctly set
  when calling create_tmp_table().
- Aria::empty_bits is not allocated if there is no varchar/char/blob
  fields in the table.  Fixed code to take this into account.
  This cannot cause any issues as this is just a memory access
  into other Aria memory and the content of the memory would not be used.
- Aria::last_key_buff was not allocated big enough. This may have caused
  issues with rtrees and ma_extra(HA_EXTRA_REMEMBER_POS) as they
  would use the same memory area.
- Aria and MyISAM didn't take extended key parts into account, which
  caused problems when copying rec_per_key from engine to sql level.
- Mark asan builds with 'asan' in version strihng to detect these in
  not_valgrind_build.inc.
  This is needed to not have main.sp-no-valgrind fail with asan.

sql/temporary_tables.cc

@@ -912,9 +912,8 @@ bool THD::has_temporary_tables()
 uint THD::create_tmp_table_def_key(char *key, const char *db,
                                     const char *table_name)
 {
-  DBUG_ENTER("THD::create_tmp_table_def_key");
-
   uint key_length;
+  DBUG_ENTER("THD::create_tmp_table_def_key");
 
   key_length= tdc_create_key(key, db, table_name);
   int4store(key + key_length, variables.server_id);
@@ -1163,11 +1162,10 @@ TABLE *THD::open_temporary_table(TMP_TABLE_SHARE *share,
 */
 bool THD::find_and_use_tmp_table(const TABLE_LIST *tl, TABLE **out_table)
 {
-  DBUG_ENTER("THD::find_and_use_tmp_table");
-
   char key[MAX_DBKEY_LENGTH];
   uint key_length;
   bool result;
+  DBUG_ENTER("THD::find_and_use_tmp_table");
 
   key_length= create_tmp_table_def_key(key, tl->get_db_name(),
                                         tl->get_table_name());