ha_innobase::change_active_index(): Clean up code formatting.

ha_innobase::check(): Incorporate the code from
row_check_table_for_mysql().  Report errors to the client connection
instead of writing them to the error log.

row_check_table_for_mysql(): Remove.

row_check_index_for_mysql(): Renamed from row_scan_and_check_index().
Let the caller initialize prebuilt, and assume that the index is usable.

rb://178 approved by Sunny Bains