When MariaDB 10.1.0 introduced table options for encryption and
compression, it unnecessarily changed
ha_innobase::check_if_supported_inplace_alter() so that ALGORITHM=COPY
is forced when these parameters differ.
A better solution is to move the check to innobase_need_rebuild().
In that way, the ALGORITHM=INPLACE interface (yes, the syntax is
very misleading) can be used for rebuilding the table much more
efficiently, with merge sort, with no undo logging, and allowing
concurrent DML operations.
* some of these tests run just fine with InnoDB:
-> s/have_xtradb/have_innodb/
* sys_var tests did basic tests for xtradb only variables
-> remove them, they're useless anyway (sysvar_innodb does it better)
* multi_update had innodb specific tests
-> move to multi_update_innodb.test