add client event for client or DR fault

_From [derek.br...@gmail.com](https://code.google.com/u/117968039472581148324/) on February 24, 2009 14:35:01_

this was PR 200414

we'll want to add an event for faults occurring in DR or client code so that
a tool can report such failures in a customized way or try to recover from
client faults.

note we still don't have a good plan for SEH across client/DR boundary -
e.g. when a client passed a NULL pointer to a DR routine we'll currently
take the blame

we already provide dr_safe_{read,write}.
xref issue #51 /PR 198875 on adding try/except.

we already provide an exception event on Windows and a signal event on
Linux (PR 304708) for application faults (both of which do not handle
faults in DR or a client, deferring to this case).

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=50_