string conversion of timestamps is broken

ps_fetch_datetime() does not work for DATETIME( n ) fields where n is between 1 and 5.

for example, when DATETIME(3) is used for millisecond resolution, the current version sprintf()s the first 3 digits of the microsecond field, but this yields a wrong output, when there are leading zeroes (see examples below).

Test values, type DATETIME(3):
2016-03-09 07:51:49.000
2016-03-09 07:51:49.001
2016-03-09 07:51:49.010

ps_fetch_datetime() output:
2016-03-09 07:51:49
2016-03-09 07:51:49.1000
2016-03-09 07:51:49.10000

See github pull requests for fixes:
master: https://github.com/MariaDB/mariadb-connector-c/pull/17
2.2.x: https://github.com/MariaDB/mariadb-connector-c/pull/16