Use 'struct bintime' instead of 'sbintime_t' to manage times in vPIT to postpone rounding to final results rather than intermediate results. In tests performed by Joyent, this reduced the error measured by Linux guests by 59 ppm. Smart OS bug: https://smartos.org/bugview/OS-6923 Submitted by: Patrick Mooney Reviewed by: rgrimes Obtained from: SmartOS / Joyent MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D20335