Fix sub-second handling in MySQL driver

As stated in http://dev.mysql.com/doc/refman/5.7/en/c-api-prepared-statement-data-structures.html
the content of MYSQL_TIME.second_part field is supposed to be
in microseconds not milliseconds.

Task-number: QTBUG-31124
[ChangeLog][QtSql][QMYSQL] Fix sub-second handling
Change-Id: I5718868029bdedab9508213e800d2dcf3da9be9a
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Mark Brand <mabrand@mabrand.nl>
Fix sub-second handling in SQLite driver

Use explicit format string, that contains milliseconds, when
converting an QDateTime/QTime to a SQLite field content.

Task-number: QTBUG-24200
[ChangeLog][QtSql][QSQLITE] Fix sub-second handling
Change-Id: Ib89152b7c3dd780b57a8826beff8b6b118e9d3d6
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Mark Brand <mabrand@mabrand.nl>