p5-DBI: update to 1.639.

Changes in DBI 1.638 - ...

    Fix UTF-8 support for warn/croak calls within DBI internals,
        thanks to pali #53
    Fix dependency on Storable for perl older than 5.8.9,
        thanks to H.Merijn Brand.

    Add DBD::Mem driver, a pure-perl in-memory driver using DBI::DBD::SqlEngine,
        thanks to Jens Rehsack #42

    Corrected missing semicolon in example in documentation,
        thanks to pali #55

(wiz)