[new compiler] Fix signal handlers for properties declared in the same object

[new compiler] Fix signal handlers for properties declared in the same object

We need to generate the property caches before we can try converting the
signal handler expressions in the AST to function declarations, as that
conversion requires looking up the signal signature / meta-data from the
property cache. This in turn requires rewriting the property cache
generator code to operate on the data structure we have before creating
the QV4::CompiledData.

Change-Id: I0d1c59d947f36171b4eb89f47a2e1ff1bc493c6f
Reviewed-by: Lars Knoll <lars.knoll@digia.com>