Investigate wallet clock skew handling

[shane-kerr]

We have some code that is supposed to handle clock skew.

static int64 nTimeOffset = 0;

int64 GetAdjustedTime()
{
    return GetTime() + nTimeOffset;
}

void AddTimeData(const CNetAddr& ip, int64 nTime)
{
   // 50 lines of voodoo updating your clock from other nodes
}

We can see this being adjusted in the debug.log file:

Added time data, samples 2, offset -40 (+0 minutes)
Added time data, samples 3, offset -17 (+0 minutes)
dded time data, samples 4, offset -17 (+0 minutes)
Added time data, samples 5, offset -53 (+0 minutes)
nTimeOffset = -17  (+0 minutes)

However it goes wonky sometimes:

nTimeOffset = -51  (+0 minutes)
Added time data, samples 64, offset -27 (+0 minutes)
Added time data, samples 65, offset -14 (+0 minutes)
nTimeOffset = -51  (+0 minutes)
Added time data, samples 66, offset -1269 (-21 minutes)

This seems bad especially since on this computer the time was within 2 milliseconds of "true" time based on NTP.

One possibility is just to report clock skew if detected, but never to adjust.

In any case, research this.