Last snapshot's time is incorrect with -time_allocs

_From [derek.br...@gmail.com](https://code.google.com/u/117968039472581148324/) on December 10, 2010 19:52:22_

PR 581817

When using -time_allocs, the last snapshot's time (in both snapshot.log and staleness.log) is 0. This is incorrect. The time for the last snapshot in this case can either be made the previous snapshot's time (not accurate) or incremented by one (which is also not accurate as an alloc event didn't happen). However, leaving it a 0 shows makes it overlap with the snapshot `#0` and thus eliminate it because the first one usually has low memory consumption (we choose the one with higher memory consumption if the time axis value is the same).

I ran into this while trying to collect data test visualization of large number of snapshots (PR 581809)

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=232_