Changing threading semantics from init early to init before second thread

[Havoc Pennington]

Robert McQueen wrote:
> This seems very appealing to me - pthreads are supposed to be the
> standard thread mechanism which everyone codes to. I even recall that
> win32 has a pthreads implementation floating around somewhere. If it's
> sufficient to allow D-Bus to do what it needs even when running in
> threads which weren't created under this abstraction, it would be
> possible for us to just require pthreads and leave it at that.
> 

It'd probably be better to abstract the windows native threads instead 
of requiring cygwin or something. It shouldn't be a lot of work.

A simple way to do this is just create dbus-sysdeps-threads.c that can 
return the "thread funcs" struct for the current platform; then we can 
just init threads with these thread funcs if the app doesn't init 
threads, will take some thinking about when exactly to do the init.

Havoc