The problem occurs because the statement generated by Spider used an
internal function name, ADD_TIME.

This problem has been corrected by the fix for bug MDEV-16878 within the
server, which enables Spider to generate the statement using the actual
SQL function name.  I have made some additional changes within Spider to fix
related problems that I observed while testing.

Author:
  Jacob Mathew.

First Reviewer:
  Alexander Barkov.

Second Reviewer:
  Kentoku Shiba.