MariaDB before MDEV-5800 in version 10.2.2 did not support
indexed virtual columns. Non-persistent virtual columns were
hidden from storage engines. Only starting with MDEV-5800, InnoDB
would create internal metadata on virtual columns.

Similar to what was done in MDEV-18084 and MDEV-18960, we adjust two more
code paths for the old tables.

ha_innobase::build_template(): Do not invoke
dict_index_contains_col_or_prefix() for virtual columns if InnoDB
does not store the metadata.

innobase_build_col_map(): Relax an assertion about the number of columns.

ha_innobase::omits_virtual_cols(): Renamed from omits_virtual_cols().