[new compiler] Add support for QML list models

[new compiler] Add support for QML list models

List model definitions make heavy use of custom parsers, which requires AST
access as well as a general port to the new QQmlCustomParser API.

Additional fixes in the custom parser support were needed to pass all tests:

 * Fix support for AcceptsSignalHandlers and AcceptsAttachedProperties
 * Don't call setCustomData unless the compiler generated data earlier

Change-Id: Ic42f8a890391267c94f63d35f055b60fdbf3c83d
Reviewed-by: Lars Knoll <lars.knoll@digia.com>