MERGE: speedup bsescm startup

[Stefan Westerfeld <stefan space twc de>]

   Hi!

I've found that bsescm startup time largely consists of g_usleeps which are
necessary to wait for bse to do something (like registering core plugins). The
function that waits for the completion of these tasks always blocks 250ms
(bse-context-iteration #t).

A better way is a proper implementation of this function, so that it just gives
up the CPU until bse is really done. I've implemented that, and both audio
tests and the filecheck test loading benefit, so make slowcheck is a bit faster
with the changes applied. Please merge:

repo:   http://space.twc.de/public/git/stwbeast.git
branch: scm-wait-with-mainloop

   Cu... Stefan
-- 
Stefan Westerfeld, Hamburg/Germany, http://space.twc.de/~stefan