report uninit error only if the full access is uninitilized

_From [zhao...@google.com](https://code.google.com/u/106321947286816917100/) on September 11, 2012 16:33:01_

There are false positives reported when running Dr.Memory.
We should add option to report uninit error only if the full access data is uninitialized, and investigate them first to
1. reduce false positives
2. figure out why if they are false positives

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=1022_