Revert "Rewrite Qt4 based nested yield mutex locking."

In a dbgutil build LO aborts on an assertion failure the moment
KFileDialog is open. It's definitely on okay to release SolarMutex just
like that, since the Qt event loop is integrated with LO's, it'll call
back to LO code without the mutex held.

This reverts commit 13a34f4c6307d1bd2443cbf3fbd83bfdd8cdbafb.

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

Change-Id: Idfa27fbb4728b529c37c25f710ea208fdaa4455c
make sure KFileDialog does not leave the SolarMutex released

Change-Id: I806bf5fe1cd1871de499ceeeadf36de539e9d637
fix Qt4 QSocketNotifier configure check

When built as a part of the configure check, this doesn't know SAL_OVERRIDE.

Change-Id: I1420dd50efdd6666f246884f286a3f29e0b56a2c
disable KFileDialog usage if QClipboard can recurse

Change-Id: If23a365b96c1634c2f8940f6ece973089dc3151f
add better info on the Qt patches needed for KFileDialog

Change-Id: I1902f962ac03b171c5e7a45d9c8e59450b04418f