Add the symbol WTFInvokeCrashHook back for binary compatibility.

Patch by Benjamin Poulain <bpoulain@apple.com> on 2013-05-16
Reviewed by Ryosuke Niwa.

* wtf/Assertions.cpp:
* wtf/Assertions.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@150228 268f45cc-cd09-0410-ab3c-d52691b4dbfc