Check module in drcov postprocessing

_From [zhao...@chromium.org](https://code.google.com/u/111879852748806430180/) on September 03, 2014 15:20:54_

It is possible that drcov runs on different builds of the same module and dump the coverage info, so on post processing, drcov2lcov should check whether the module for symbol info is the same module when drcov information is collected.

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=1535_

Start at the drcov2lcov postprocessing entry point and trace how collected coverage information is matched with module symbol information. Confirm how the module identity is represented in both inputs; done means mismatched modules are detected rather than combined silently.

Written by the indexing model from the issue text.