Bug#36751: Segmentation fault in ctype-bin.c:308; Linux 86_64, with-max-indexes=128

mysqld is optimized for the default
case (up to 64-indices); for a greater
number of indices it goes through a
different code path. As that code-path
is a compile-time option and can not
easily be covered in standard tests,
bitrot occurred. key-fields need an
explicit initialization in the non-
optimized case; this setup was
presumably not added when a new key-
vector was added.

Changeset adds the necessary
initialisations.

No test case added due to dependence
on compile-time option.

sql/sql_select.cc:
  Init merge_keys as well. If we don't,
  things blow up badly outside of the
  optimized-for-64-keys case!
sql/table.cc:
  Init merge_keys as well. If we don't,
  things blow up badly outside of the
  optimized-for-64-keys case!

sql/sql_select.cc

@@ -9788,6 +9788,7 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
   table->in_use= thd;
   table->quick_keys.init();
   table->covering_keys.init();
+  table->merge_keys.init();
   table->keys_in_use_for_query.init();
 
   table->s= share;

sql/table.cc

@@ -1652,6 +1652,7 @@ int open_table_from_share(THD *thd, TABLE_SHARE *share, const char *alias,
     goto err;
   outparam->quick_keys.init();
   outparam->covering_keys.init();
+  outparam->merge_keys.init();
   outparam->keys_in_use_for_query.init();
 
   /* Allocate handler */