#39 PostgreSQL quoting of datetime and time broken

[Stuart Bishop]

Passing datetime to sqlrepr results in truncation of the time
portion. Passing a time to sqlrepr results in corruption.

>>> sqlrepr(datetime(2003, 12, 4, 13, 45, 50), 'postgres')
"'2003-12-04'"
>>> sqlrepr(date(2003, 12, 4), 'postgres')
"'2003-12-04'"
>>> sqlrepr(time(13, 45, 50), 'postgres')
"'13:45:-1'"