streams and async stuff

[Maciej Stachowiak <mjs eazel com>]

We found a way to partly work around this problem in Nautilus rather
than embarking on large Bonobo changes at this late a date. I still
think it is a serious architectural flaw, but it's too late to fix it
for Bonobo 1.0 (especially since Bonobo is supposed to be more or less
API frozen by now).

In brief, we're going to use a separate process which will implement
the Streams and feed the data to the component. This will avoid
blocking the nautilus UI, but the UI of the individual components can
still block. In the future we'll probably switch to threads for
handling this.

 - Maciej