NDB cluster is not fully supported. This will be added with
WL 1892 (NDB Handler: Add support for CREATE/DROP INDEX).
Some preparatory code for this is already present though.
A change for the "duplicate key" error message is planned
for another changeset.


include/my_base.h:
  WL#1563 - Modify MySQL to support fast CREATE/DROP INDEX
  Defined a mask of flags which must be the same for two indexes
  if they should compare as compatible.
  Added an error number for a new drop index error message.
mysql-test/r/key.result:
  WL#1563 - Modify MySQL to support fast CREATE/DROP INDEX
  The test result.
mysql-test/t/key.test:
  WL#1563 - Modify MySQL to support fast CREATE/DROP INDEX
  The test case.
sql/handler.cc:
  WL#1563 - Modify MySQL to support fast CREATE/DROP INDEX
  Prepared for a later change in an error message:
  Replace index number by index name for "duplicate key" error.
  Added handling for the new drop index error message.
sql/handler.h:
  WL#1563 - Modify MySQL to support fast CREATE/DROP INDEX
  Added new flags and methods.
  Removed old flags and methods (from the last attempt).
sql/share/errmsg.txt:
  WL#1563 - Modify MySQL to support fast CREATE/DROP INDEX
  Added a new error message for drop index.
sql/sql_table.cc:
  WL#1563 - Modify MySQL to support fast CREATE/DROP INDEX
  Moved definitions to the top of the file.
  In mysql_prepare_table() allow an index to have the name
  "PRIMARY" if it has the key type "Key::PRIMARY".
  Added a parenthesis for readability.
  Removed old code from the last attempt.
  Some changes to compare_tables():
  - Input parameter "List<Key> *key_list" is replaced by
    "KEY *key_info_buffer, uint key_count".
  - Output parameters added: "index_drop_buffer/index_drop_count"
    and "index_add_buffer/index_add_count".
  - Key comparison must now find matching keys in changed
    old and new key lists.
  - Key comparison of a key is easier now because both old
    and new keys are of type 'KEY'.
  Call mysql_prepare_table() before compare_tables(). The
  translated KEY structs are needed at some places now.
  Inserted a code segment for checking alter_table_flags().
  Removed mysql_prepare_table() from the 'partition' branches
  (it is done above now).
  Removed a pair of unnecessary braces.
  Inserted a code segment for executing fast add/drop index.
  Made close of table dependent on whether it was opened.
  Prepared for NDB cluster support.
  Fixed commit to be called outside of LOCK_open.