Handle leaks should only report on normal exit

_From [zhao...@google.com](https://code.google.com/u/106321947286816917100/) on February 15, 2014 11:17:06_

When a process exit abnormally, e.g., assert or something, it is normal that handles are not closed, for which case, we should not check the handle leaks at all.

How do we decide whether a process exit normally or not, checking error code?

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=1443_