dbus_g_thread_init()

[Havoc Pennington]

The only suggestion I have is that there were assertions that mutex_new 
etc. were provided at the beginning of dbus_threads_init, but it should 
be allowed now to omit those if you have the recursive mutex functions.

So maybe change the assertions to be that either all recursive mutex 
functions are provided, OR all nonrecursive are provided, but not both.

Then people can stop providing the deprecated functions, and if they 
provide both they will get a warning that it makes no sense to provide both.

Looks good to me though otherwise.

Havoc