Make odbc adapter return fractional seconds in timestamps

This doesn't change the default input string to include fractional
seconds in timestamps, since we can't be sure if the underlying
database supports that.
Add 3 milliseconds on timestamp format

MSSQL will support 3 millisecond decimal places
Minor fixes for odbc/mssql fractional second timestamps

Use a timestamp format that will work on ruby 1.8. Remove related
guards from mssql adapter spec.
Fix mssql guards in integration tests

Some of these guards are only necessary for a specific adapter,
in which case they were made adapter specific.  Some of these
don't need guards at all on Microsoft SQL Server 2012, so I removed
those guards.