Timer: make parent not read-only for now

[ChALkeR]

Some parts of QmlWeb set .parent property directly, that was causing a
conflict and an exception was being thrown.

Long-term, we should create a better fix, but this fixes the immediate
problem for now, and properties not being read-only when they should
causes much less damage than unexpected exceptions on valid qml code.

This still need a testcase.

[stephenmdangelo]

I have this fix on a branch of mine that solves the issue for QObject.$delete. Are there other places you're seeing an exception being thrown for Timer?

stephenmdangelo@d20d820

[ChALkeR]

@stephenmdangelo Thanks! I will test that commit soon (hopefully today) and will tell you if that works for my original testcase that was failing (it's not a minimal testcase yet).

[ChALkeR]

@stephenmdangelo Full grep:

src/modules/QtQuick/Item.js:        child.parent = this; // This will also add it to children.
src/modules/QtQuick/Repeater.js:    this.parent = meta.parent;
src/modules/QtQuick/Repeater.js:      newItem.parent = this.parent;
src/modules/QtQuick/Loader.js:    qmlComponent.parent = this;
src/modules/QtQuick/Loader.js:    this.item.parent = undefined;
src/modules/QtQuick.Controls/ScrollView.js:      newItem.parent = this;
src/qtbase/QObject.js:    this.parent = undefined;