Per fsp0types.h, SDI is on tablespace flags position 14 where MariaDB
stores its pagesize. Flag at position 13, also in MariaDB pagesize
flags, is a MySQL encryption flag.

These are checked only if fsp_flags_is_valid fails, so valid MariaDB
pages sizes don't become errors.

The error message "Cannot reset LSNs in table" was rather specific and
not always true to replaced with more generic error.

ALTER TABLE tbl IMPORT TABLESPACE now reports Unsupported on MySQL
tablespace (rather than index corrupted) along with a server error
message.

MySQL innodb Errors are with with UNSUPPORTED rather than CORRUPTED
to avoid user anxiety.

Reviewer: Marko Mäkelä