Revert "KDE4: sleep in yield for native file picker"

This reverts commit 380f3b4b6cbbe8e82b58ddf55e95c5005307b51f.

Conflicts:

	vcl/unx/kde4/KDEXLib.cxx
	vcl/unx/kde4/KDEXLib.hxx

Change-Id: I8a201c89be63cebab7401124002261be23e049c7
Revert "fdo#67011: Run Display::Yield through KDEXLib::Yield."

This reverts commit 95f60222e75486336b6569afa8f34d60b51c94ad.
Revert "Rewrite Qt4 based nested yield mutex locking."

This reverts the unx/kde4/KDEXLib.cxx part of

commit 13a34f4c6307d1bd2443cbf3fbd83bfdd8cdbafb.

Conflicts:

	vcl/unx/kde4/KDE4FilePicker.cxx
	vcl/unx/kde4/KDEXLib.cxx

Change-Id: Ica8a0f678f080ae7d763bb7da7761d20ceec328c
KDE4: change eventLoopType enum to glib bool

Just check for glib; it's the default in later Qt4 versions on unix.

Change-Id: Ia99466e9010eb835bea0c3c4420da3c8b3cd4671
KDE4: add Qt4 glib ExcludeSocket runtime check

Add a runtime check and configure warning to disable KDE4 native
file pickers, if the Qt4 glib dispatcher doesn't honor the
QEventLoop::ExcludeSocketNotifiers flag.

This way polling the QClipboard using the event loop won't
crash LibreOffice with recursive paint events,

See https://bugreports.qt-project.org/browse/QTBUG-37380

Change-Id: I5cad30ead74571e49a075c084cca7a19acff7523
KDE4: prevent blocking in Display::Yield

SalX11Display registers a Yield handler, which splits check and
and processing into two functions, which both lock the yield mutex.

Normally this no problem, but during a Drag'n'Drop operation the
D'n'D thread also checks and processes XEvents (for D'n'D). So the
XNextEvent in Display::Yield will actually block, if the seen XEvent
was for D'n'D and was already processed.

Change-Id: I9f8d96d4f9986997cbe150a2b66bc767b4bbc2f1