Make the timeouts behave as they ought.

Make the timeouts behave as they ought.

Each platform has its own API for high resolution timers, so I added an
abstraction function that returns a monotonically increasing number in
nanoseconds.

On Windows, we use QueryPerformanceCounter()
On OSX, we use mach_absolute_time()
On Linux, we use clock_gettime() with CLOCK_MONOTONIC

Signed-off-by: Drew Fisher <drew.m.fisher@gmail.com>