API change / addition to distinguish fork and vfork

_From [peter.goodman](https://code.google.com/u/peter.goodman/) on October 07, 2013 17:47:39_

What is the problem to solve? Why is it important? Provide some context for those unfamiliar with the details of the system. XREF issue #1288 . What are the possible approaches to solving the problem? - Status quo: don't distinguish them.
- Extra parameter (e.g. bool) to current fork_init event.
- Current fork_init_event only called for non-shared case, new event added for shared memory case.
- Current fork_init_event only called for non-shared case, new event added covering both shared/non-shared cases with a distinguishing parameter. Which approach is being taken and why? Current approach does not distinguish vfork and fork (status quo). Any interesting details or challenges of the implementation? Backward compatibility should be considered when making API changes/additions.

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=1289_