Qt5: Compile when Qt Designer library not found
Qt5: Remove QT_{BEGIN,END}_HEADER macro usage

See:
http://lists.qt-project.org/pipermail/development/2013-January/009284.html
Qt5: Fix warnings

The signature of QItemEditorFactory::createEditor(...) now wants an int
instead of a QVariant::Type argument
Fix crash in ModelCellModel
Protect against QMetaObject deletions

QML types in QtQuick set dynamic meta objects on QObject instances,
in this case QObject::metaObject() no longer returns the pointer to the
static meta object, but to a meta object created at runtime.

For now, ignore dynamic meta objects in the meta object browser
altogether.

Good: No longer crashes in case meta objects got deleted
Bad: No longer shows QML types in the browser

TODO: Detect deletions, e.g. by ref-counting the meta object (check the
number of QObject instances depending on it).