Fractional seconds support

[tchaloupka]

I did not found the way to read values to SysTime type. There is only DateTime conversion but it doesn't support fractional seconds.

Only mention to fractional seconds in code is here:

mysql-native/source/mysql/protocol/packet_helpers.d

Line 46 in 469f9c6

// Note that the fractional seconds part is not stored by MySQL

which states, that MySql doesn't store it, but it is not true with v5.6 and newer as described in: https://dev.mysql.com/doc/refman/5.7/en/date-and-time-type-overview.html (was with 5.5)

[schveiguy]

@Abscissa sorry to bug you, but was this added?