This is like boinc_init() but for multithread apps.
Unlike boinc_init(), it suspends/resumes all threads in the app,
not just one.
In Unix, this is done by forking,
and having the parent process handle suspend/resume messages
and suspend/resume the child using signals
On Win, there's some nasty code that enumerates all
threads in the whole system, and suspends/resumes
those in a particular process.
svn path=/trunk/boinc/; revision=20054