Upstream bug: uv_hrtime() return non-incremental value under windows

[mschauer]

I was puzzling why the elapsed macro is not working correctly under windows.

It turns out that this is an upstream bug in libuv, I leave a note here if somebody runs into the same problem: uv_hrtime can return non-incremental values under windows resulting in underflow of (time_ns()-t0)/1e9 in the elapsed macro.

Compare joyent/libuv#850.

[StefanKarpinski]

Excellent sleuthing tracking down the cause to that libuv bug.

[vtjnash]

Since that has a patch, we can just apply that to our local branch and get the fix without waiting for upstream

[timholy]

Long ago I had to fix what was basically this same libuv bug on multiple Unix systems; I guess I didn't fix the Windows version at that time because timers are different on Windows, I lacked a Windows system to test on, and this was back before we had a Windows port. But with hindsight...

[mschauer]

Fixed upstream, joyent#850

[vtjnash]

pulled in the upstream fix in 5bf16a9