Add ToSql/FromSql for time::Timespec.
Add ToSql/FromSql for time::Timespec.

Uses SQLite's default format string for `datetime()`.

huonw/rusqlite,mikelodder7/rusqlcipher,gwenn/rusqlite,gwenn/rusqlite,pfernie/rusqlite,jgallagher/rusqlite,xinghun92/rusqlite,cmsd2/rusqlite,xinghun92/rusqlite,jgallagher/rusqlite,xinghun92/rusqlite,mikelodder7/rusqlcipher,mikelodder7/rusqlcipher,jgallagher/rusqlite,gwenn/rusqlite