[Mantisbt-dev] small schema.php request

[Gianluca S. <gi...@gm...>]

I don't think it's a great problem in itself but, since AFAICT the
schema.php file is modified only by appending stuff at the end, it
could make sense to mark the releases with appropriate comments.

This could be useful for reference purposes and easy tracking when a
given schma change was done.