DropIndex, CreateIndex: Remove. The file row0trunc.cc only exists
in MariaDB Server 10.3 so that the crash recovery of TRUNCATE TABLE
operations from older 10.2 and 10.3 servers will work. This dead code
was being used for implementing the MySQL 5.7 WL#6501 TRUNCATE TABLE
that was replaced with a backup-safe implementation in MDEV-13564.