force posted events before timer timeouts in KDE4 event loop (bnc#467278)

In this particular case, basctl::Shell::onDocumentCreated() and pretty much
everything in basctl/ it seems operate on the current window. The "OnNew"
event that triggers this comes from a timeout generated who knows where
for whatever reason. However, the code "knows" what the current window
is by having basctl::Shell::SetCurWindow() react on events about the current
window changing ... which come from posted events.

So, unless it's defined somewhere that an ordering here must exist, this
is inherently racy. At least generic and Gtk event loops appear to always
deliver the posted event first, so force the same ordering in the KDE
event loop handling.

Change-Id: Ia098f6b45e6b5a5133a12a9172eb09069e6362f9