Allow caller to set the algorithm that will be used for DDL ALTER TABLE operations

[chitty]

Allow callers to set the algorithm that will be used for DDL ALTER TABLE operations instead of hardcoding it to INPLACE.

There is a DDL limitation where using the INPLACE algorithm fails, and COPY should be used instead:

Tables created before MySQL 5.6 that include temporal columns (DATE, DATETIME or TIMESTAMP) and have not been rebuilt using ALGORITHM=COPY do not support ALGORITHM=INPLACE. In this case, an ALTER TABLE ... ALGORITHM=INPLACE operation returns the following error:

ERROR 1846 (0A000): ALGORITHM=INPLACE is not supported.
Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY.

There was also an issue reported earlier in which using the INPLACE algorithm fails, and using COPY is recommended by the resulting error message.